She's had a big shock.
She HAS been the centre of your world and now she feels that position is threatened and that you have betrayed her.
In a year she's had to adapt to your partner moving in (and sharing you with him) and now your attention (and love from her POV) is being diluted further.
I'm an only child and if my parents (never mind parent/step parent) had told me I was going to have a sibling at 14 I'd have found it hard to process.
This isn't a sibling she's going to be best friends with/hang out with. It's a cute baby that's going to demand all your and everyone else's attention. She's probably scared shitless that she will become second best.
Your joy at the prospect of a new baby is not something you can/should have assumed your DD would share.
You say a lot in your post about how it's affecting you and how you feel about the baby. Not much reflection on how the pregnancy might have impacted her. That's something you need to change.
You can't force her to talk to you but you can communicate with her.
Maybe write her a letter? BUT if you do, centre her feelings not yours.
Say you are sorry you didn't prepare her better for this news. Make clear that the bond you have isn't diminished by another child and how much you love her.
Be clear that you are happy to talk about this and how involved she wants to be in your pregnancy/siblinghood - she's old enough to be given a significant degree of self agency here.
Ask her what her fears are. Listen to them.
Don't assume all will be well when the baby is born. You need to address this now.