From one cat person to another, congratulations on the new addition! Kittens are awesome.
Only you know the particulars of your situation... but if your mom has a history of ignoring, invalidating, and making degrading comments about things that matter to you (unless she shares an interest), my suspicion is that confronting her about her behavior probably isn't going to change things for the better.
I ended up with my first kitten as a teenager, when our family took in a pregnant stray. There were complications, and one of the kittens was not expected to survive. A friend taught me how to tube feed the kitten and give him subcutaneous fluids. Somehow, he managed to beat the odds. We were inseparable, and that kitten quite possibly saved my life. I was told that I could keep him.
Once it finally hit NDad how much the kitten meant to me, he threatened to give it away, claiming that a coworker wanted one, he was going to "give her the first pick" and there was "nothing I could do about it". (We all knew which kitten was likely to go first.) Fortunately, EMom intervened... and, as it turned out, nobody actually wanted a kitten. NDad was just being NDad.
I lost one of my cats earlier this year, following a prolonged illness. NDad did not acknowledge the cat's passing, despite the fact that EMom texted him about it and he'd seen a post about it on facebook. He went out of his way to avoid me until dinner (NDad doesn't tolerate any expression of emotion), when I was (literally) screamed at before I even made it to the table for mentioning that the GC used to like mushrooms. "Shut up, shut up, just SHUT UP! I will NOT have you discussing your brother like this when he isn't here!" [Translation: I am busy enjoying my dinner and bragging about a conversation I had with your brother. (He is always competing with EMom over who has the most contact with the GC) I am having a good time, and I do not want to have to acknowledge you or your stupid dead cat. Stop inconveniencing me and go away.] The fact that he doesn't care is probably always going to hurt... but it's also probably never going to change, so I am trying to learn to ignore it the best I can.
I'm sorry you're going through this. Narcissistic parents suck. Yay, cats?