AITAH for rehoming a kitten that my friend has ignored?

My (31f) boyfriend’s (29m) cat had kittens in July. My bf lives with his uncle in a small house along with his aunt, cousin, and his uncles friend. Momma cat had five kittens, at first the cousin wanted to keep them but as they got older she refused to take care of them properly so my bf and I stepped in. In exchange we claimed the kittens as ours. As they got bigger his uncle told us that they needed to go, they’re too big and too many. He also was actively trying to rehome momma cat.

I started asking friends and coworkers if they wanted a kitten for cheap, my bf and i had each picked a kitten to keep. One of my coworkers took a kitten, and one of my friends took a kitten.

Let’s call this friend Siv (30f). Siv and I agreed that I would foster her kitten until she moved into a pet friendly place, time limit one year. We also agreed she would pay me at the beginning of every month for expenses for her kitten, with the understanding that rhe price would increase as she got bigger, and that she would pick up the kitten one day on the weekends.

Everything started out fine, Siv and her friend Andy would come pick up the kitten every Sunday and we would take her home. I was unaware that they were only playing with the kitten in Andy’s car, not letting the kitten out unless it was to use the bathroom. When I found out I made a point to tell Siv that she couldn’t keep doing that and the kitten needed more space to play and explore. As time went on Siv started canceling her weekend pick ups in favor of doing other things. She was sick and didn’t want the responsibility, she wanted to go to the Ren fair, a few times she just no showed and didnt communicate. At the end of October I blew up at her, told her that what she was doing wasn’t fair to me or the cat and she had agreeded to every weekend with the exception of two holidays.

She blew up on me the following weekend because I didn’t allow her to come get the kitten after she didn’t show for three weekends in a row. Cussed me out and then turned the anger towards our friendship which was rocky at best. After that I told her that she could communicate with my bf about pick up and all things kitten related and stepped away from it. She hasn’t come to pick up the kitten or payed for the month.

Here’s where I might be the AH. My coworker, who adopted one of the other kittens asked if I still had any, her friend was looking for one and I said yes. I gave S’s kitten to the coworker. S has since asked to come see the kitten and my bf told her no, that she hasn’t kept her end of the deal. She showed up anyway last weekend and flipped her ish when she realized I gave her kitten away and started to demand I let her have one of mine. I shut her down and threaten to call the cops if she didn’t leave. So AITAH?