It's because you're afraid of being hurt again. If she completely shuts you out again, its more protective to feel that you "didn't feel much" to begin with anyway because you now "resent" her company and don't look forward to her coming over again - so if she does leave then she can't hurt you all over again. And you're probably not excited for the baby for the same reason - you're worried (even subconsciously) that if you do get excited history might repeat itself and she'll cut contact.

Don't have a conversation with her about not feeling excited about the baby. That could crush her and make the gap even worse. You'll have to put on your grandma face when bubs is born for the long term health of all of your relationships.

There's no "boundaries" per say and as it's been the longest you've seen her at her place she probably likely did feel like she'd come to a hotel for a break and let mom run around after her especially given that she's pregnant. I don't for one second say this is right, but if she hasn't lived with you for years she's lost the appropriate way she's meant to be acting when staying at yours. Again - not a conversation I'd bring up with her, given how estranged your relationship is.

What I think is that you do need counselling to work through the feelings that you are experiencing. You have to heal first before you can move on with her. And hopefully in time when you've worked through the hurt you'll begin to feel more like the person you felt before all of this happened.