Woman says she let her younger sister live with her for free while she went to college — and months after the baby-waking keypad fight, the final straw was finding her diaper bag packed for a beach trip like it was communal property

A 25-year-old woman on Reddit said she thought she could make living with her younger sister work if she just kept the rules simple enough.

She wrote that she lived in a three-bedroom apartment with her fiancé and their six-month-old son. Her younger sister, Mia, 20, had started attending a university closer to the woman’s home than to either parent’s house, so the woman and her fiancé let her move into the spare bedroom in January. Mia was living there for free, at least for the time being, with the plan that she would eventually contribute a small amount toward rent once she got a job.

From the start, there was one especially important rule. The apartment door had an electronic keypad lock and a normal key lock underneath it. Everyone had keys, but they usually used the keypad because it was easier. The problem was that the keypad made a lot of noise, and the nursery was close enough that any late-night beeping woke the baby up. So the woman told Mia from day one that she could come home however late she wanted, as long as she used her key and stayed quiet after the baby went down, usually between 7 and 8 p.m.

At first, Mia followed the rule. Then college social life kicked in. The woman wrote that over the month before the first post, Mia had been coming home after midnight every Friday and Saturday, forgetting the rule over and over, and using the keypad anyway. Each time, the baby woke up crying. The woman would sit Mia down, remind her of the rule, and Mia would promise to be more careful. Nothing changed. Eventually, the woman got so fed up that she changed the keypad code and told Mia she was no longer allowed to use it at all. Mia agreed.

Then came the night that pushed the situation into public-Redit territory. On a Friday night, Mia went out with her friends, got very drunk, came home at 4 a.m., forgot the code had been changed, and punched in the wrong code enough times to trigger the alarm. The baby woke up crying, and on top of that, neighbors complained about the noise. The next morning, the woman said she lost it and told Mia there would now be a curfew: while living there, she had to be home by 8 p.m. and was not going out at night for the rest of the semester. Mia argued that her sister had no right to “ground” her, but the woman held the line and said that if Mia wanted complete freedom, she could have it in her own place, not in a home where other people were losing sleep because of her. Their mother and stepfather sided with the woman. Their father sided with Mia and said she was overreacting to a drunken mistake.

At the time, the woman still thought the issue might be fixable. In comments on the BORU thread, she said she was being “nice exclusively” because Mia was going back to therapy, which had helped her before she quit. She made it clear this was the last chance: if Mia pulled anything like that again, she was out.

For a while, things did calm down. Then in June, Mia started sliding back into old habits. In the five-month-later update, the woman wrote that it began with smaller entitlement. Mia took her things without permission, whined whenever the baby cried, and complained about having to “do everything,” even though “everything” basically meant her own laundry. The woman said it was annoying more than unbearable, so she mostly handled it by taking her things back and letting Mia deal with the consequences of her own messes.

The final straw came in early September.

Mia left for a beach holiday with friends. The day after she left, the woman realized her diaper bag and one of her son’s blankets were missing. Both were expensive baby-shower gifts from her best friend. She searched the apartment and eventually found the diaper bag emptied out on Mia’s bed, with all the contents dumped elsewhere. Mia had taken it as extra luggage because, according to her later explanation, she did not want to empty her school bag and her computer would not fit anywhere else. The blanket had been tucked into one of the bag’s pockets, so it got taken too “by mistake.” When the woman finally got both items back, they were dirty and full of sand.

She called Mia immediately. Instead of apologizing, Mia justified it and then called her “dramatic” when she asked for an apology. That was it. The woman told her that when she came back from the trip, she would have one week to get her things and move back in with one of their parents. Mia spent the rest of the trip trying to argue her way out of it and also tried to recruit the parents. Their mother told Mia she had brought it on herself. Their father once again tried to talk the woman into being “nice,” but she told him she already had been. When Mia got home, she tried to pick a fight, but this time the woman did not budge.

Mia officially moved out a couple of weeks later. The woman wrote that their mother was making Mia save money so she could pay back the nearly eight months of rent she owed. In the update, the woman sounded much more exhausted than angry. She wrote that being the older sister had always felt like being a second mother without any of the authority of an actual parent. She said her mom acknowledged she had effectively been Mia’s third parent growing up, especially after the divorce. Their father, on the other hand, refused to understand how much responsibility had fallen on her. She also wrote that Mia had always treated her like an afterthought: using her for rides, giving her insulting birthday gifts, and contacting her mostly when she needed something.

So what started as a drunken late-night keypad disaster and a baby waking up over and over ended with something much deeper being exposed. The diaper bag was just the point where the woman stopped trying to act like Mia’s disrespect was a phase she could mother her out of. She had let her sister live there for free, bent over backwards to make it work, and even given her a final chance after the alarm incident. The beach trip proved Mia still saw her sister’s home, her time, and even her baby’s belongings as things she could use without asking — and that was finally enough to get her kicked out.