Need advice my sis has too many pets and my dad just bribed her with another one.?

My sis currently has 3 hamsters and 1 cat that all sleep in her bedroom the hamster cages barely get cleaned out and they smell when I walk past them so I clean them and change their food and water. I'm constantly checking on her hamsters and feeding them making sure they are alive because all my sis does is... show more My sis currently has 3 hamsters and 1 cat that all sleep in her bedroom the hamster cages barely get cleaned out and they smell when I walk past them so I clean them and change their food and water. I'm constantly checking on her hamsters and feeding them making sure they are alive because all my sis does is hold one of them now and then.

I have my own hamster to care for right now I have 2 hamsters in my room and a cat because I'm currently looking after a hamster for a friend but with mine I clean them out every week and change their food and water every 2 days so mine barely smell I used to have another hamster 2 weeks ago but he died of old age.

Our dad tried to get me to take this Gerbil from someone he knows but I said no because I don't want another pet and the house has no room for another one but then he ignores everything I just said and goes and asks my sister just because she was sad and she said she would have it but she only got a hamster about a month ago who she has already lost interest in.

What should I do I really don't want her to have another pet because she literally pays for nothing or does anything to care for them our gran pays for everything for her and she cleans them out when she can be bothered to but sometimes they will go 3 weeks without being cleaned by either of them.

What do I do?
Update: Thanks guys and I know she shouldn't own any if she isn't going to care for them correctly, I'm thinking about moving some of them into my room where they would be cleaned out everyday and have clean food and water every 2 days. I'm just worried that If I did this my sis would think that she could... show more Thanks guys and I know she shouldn't own any if she isn't going to care for them correctly, I'm thinking about moving some of them into my room where they would be cleaned out everyday and have clean food and water every 2 days. I'm just worried that If I did this my sis would think that she could get even more pets because she has the room if I removed some of her hamsters into my room :/

Also Daniel.G your pet skunk sounds adorable XD
Update 2: Actually Star of Darkness I bought and adopted all of my pets my self, I pay for everything with my own money for my own pets including vet bills, food, litter, toys, treats, cages, litter box and much more so next time ask first instead of making such an accusation. Also I don't care that she has more than... show more Actually Star of Darkness I bought and adopted all of my pets my self, I pay for everything with my own money for my own pets including vet bills, food, litter, toys, treats, cages, litter box and much more so next time ask first instead of making such an accusation.

Also I don't care that she has more than me if I really wanted another pet I could go out and adopt or buy one since I have my own money that I earn by making stuff and selling it on eBay.....
Update 3: Also Star of Darkness I did leave her hamsters alone for a month to see if she would finally grow up and care for them like she is supposed to but she didn't even feed them my gran had to feed them and when we said to her its time to clean them she said she couldn't be bothered so If myself and our gran... show more Also Star of Darkness I did leave her hamsters alone for a month to see if she would finally grow up and care for them like she is supposed to but she didn't even feed them my gran had to feed them and when we said to her its time to clean them she said she couldn't be bothered so If myself and our gran didn't care for them they would all die.
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