I'm doing to dump my friend but keep the kitten she asked me to watch for them.
Why would you dump them and then still keep their kitten?
I could tell the pet was being abused and I can't believe they would do that to an animal.
It's understandable to want to protect the animal but you have no proof that the animal is being abused so it is not okay to keep their animal. You should never keep something that doesn't belong to you. Instead you should return the animal and report possible abuse anonymously.
What? I'm sure the animal is being abused. I want to save it!
I'm glad that you are very concerned about the welfare of the animal, but it's unfortunately it still is not yours. Instead you should report the abuse to the local authorities so that they can do a proper investigation.