In that case the cat belongs to you. You asked if she wanted the Cat and she said she could not take it. I assume she never said you can look after it temporarily or that she would be back to collect it. If not then it is your cat, you now own it.
She can be abusive as she wants and even if she tries to take the matter to Court the Judge will want to know if she was that bothered about the Cat why did she leave it 11 months.
There is no excuse and unless she said it was a temporary thing you can keep the cat.
Can I clarify anything about this for you today please? Alex