what I think was a night terror,
Definitely sounds like it. This is one area I do have experience in as DS suffers badly with them (much better these days though thankfully). It is ALWAYS down to OT with him, always. Is she OT?
I'm just so tired (33 weeks pregnant).
I bet you are tired, but I think you will be even more tired if tackling this with a newborn taking every ounce of your energy too. You definitely need to get her sleeping independantly before your new LO comes along.
When do you think my husband should start going to her in the night?
As I said, I'm not experienced in SA or GW, but I would definitely say your DH needs to get involved. Whether you need to be there in the background to start with, or maybe the other way round - he is there in the background to begin with and gradually takes over with what you are doing. Does that make sense? For your own sake as much as hers, you need to get her to a point where she will respond to others as well as you - you are going to have another LO taking your attention very soon, you can't be in 2 places as once.
It seems to me as though you are definitely on the right track, keep at it, make sure you are doing things as it is suggested in the posts on this forum, and monitor the effect. Keep me posted and I will help where I can. If you need further advice we can get some other eyes in here, or maybe get a new thread posted on the relevant board depending on the issue at the time.
Hope you have another good night