Well, to start off this story I recently bought my mom's betta a new tank, 2-3 weeks ago approximately. It was a 3 gallon with a filter, and I tried to tell her to get a heater but she hasn't yet.
About a week ago, my mom purchased 2 little danio fish and put them in the tank with her betta. I told her it wasn't such a good idea, that her betta might get really stressed, and it wasn't proper room for them since she only had 3 gallons...she didn't really care, brushed me off.
Come a few days ago, I see the betta's tail in the worse shape I've ever seen it. It's jagged, looks ripped, and it disappointed me. I tried to tell my mom, and she showed concern but didn't say too much about it.
Come yesterday, a danio fish was dead and her betta was flaring and biting at the dead body.
Now, come today she tells me she doesn't like her betta anymore and doesn't want it in the tank anymore, because she doesn't want the other danio fish to die.
Long story short, I told her I'd take it and she could stock up on her precious danio fish. I feel like she doesn't really care for her betta at all... It doesn't even have a name. It kind of makes me angry, because the only reason I gave her that 3 gallon tank was for the better care of her betta!
Either way, I'm going to give him a better home. He was a precious white veiltail before, and I hope he regains his fins back well... I don't really have a tank for him yet

I only have a 1 gallon hospital tank for my current Sprinkles in case he was to get sick. He'll be getting a new home soon though, hopefully...
He's otherwise looks healthy besides the fin issue, which I'm glad for.
I just felt like ranting about this, so thanks for anyone that read this. Helped get my nerves calmed.