Am I in the wrong for feeling this way?

I've been with my SO for over 4 years. We live together and have a baby on the way.

Every since I met him, he had alot of issues with he's mom. She can be such a (sorry for my language) BITCH! I've been there for him when she hasnt.

She forgets he's birthday, if she has a gathering at her home he is never invited. Even when tho we live in the same building smh.

last year I texted her that it was he's bday because she had forgotten. And she came up to our home with a plastic bag with easter cupcake liners. As a gift

A gift is a gift and should be thankful but cmon.

(he doesn't bake by the way)

So recently she has been talking to him and out of nowhere is blowing me off to be with her. I'm mad I'm jealous idk what I'm feeling but I feel like she doesn't deserve it.