Is this animal abuse?

Okay so I'm putting this in cc because I'm not sure about it. My sister has two kittens that she keeps locked up in her (VERY hot) bedroom. She keeps the lights off and dark curtains over the windows when she's not home. However, she's NEVER home! She 17 and has a car so she just stays gone to who knows where. Anyway she never feeds these poor kittens or gives them water but some of us others in the house usually feed them and give them water whenever we can hear them meow. They're always so desperate to get out of her room but she always throws a fit whenever someone lets them out ("they're my kittens don't touch them!"). They're not starving because of the other family members that feed them but I personally just don't feel right about them being locked up in that hot room (it's summer in Louisiana and outside temperatures are reaching 100 degrees at this point) with often no water and in the dark. She wasn't even supposed to keep these kittens anyway. They were the product of a cat she secretly had and didn't fix and therefore got pregnant. I feel like she's at least neglecting these poor things. What do you guys think? (if this is in the wrong group please move it)