I am furious that my friend is engaged and having a baby with my ex
So...are you jealous that your ex is happy with someone else?
No I'm jealous because she could've picked anyone else besides my ex
I understand why you would be upset. You probably still have feelings for your ex and this conflicts with your being.
Do you think it's possible to be both happy for my friend and mad at them?
Yes, not every situation is black or white. If you still have feelings that are bothering you you should try to talk with a therapist or tell them how you feel.