Try to make her an important part of everything... I'm sure you probably already do but if he takes your hand to help you, maybe he can ask her to help too. If nothing else, it might take her mind off of being jealous because she'll be busy "being a big girl". If you and your husband are going in for a kiss, maybe make it a family hug or sandwich the little one in between. I don't know, I could go on and on but the point is, make her feel like she is extremely important too.
We did it with our 2 1/2 yr old when we were expecting again. She was number 1, even when baby came we put her to work with all kinds of important jobs (getting a toy, diaper, helping wash baby, helping change, helping pick out clothes), kept telling her that the baby loves her so much and that we need her, she's such a big help, etc. etc.
It worked, she's 4 and baby is 15 months and they adore each other. Never had any jealousy... maybe I'm just lucky though. :) I'm sure it will pass, good luck and congrats on your new baby!
I just realized something.
You mention you are 8 months pregnant. I am sure your daughter knows this and knows another child is coming in to the family.
So let's look at this from her perspective:
-- Mommy already has another child -- its in her belly and she can see it, and now
-- Daddy is helping Mommy-- so who's left for her? Where does she fit in?
This might be why she is acting so terribly insecure. Its how she feels. Again, not sure what the best approach is here in terms of how to make a 21 month old feel more secure - Just a thought.
This is a normal stage of feeling -- the oedipus complex for girls -- but two things make it different in your case
-- 21 months-- way early
-- as long as you can remember -- way too long
-- crying for 10 minutes straight-- way too much
Your daughter must feel insecure somehow -- and this does not mean that its because of anything that anyone is doing -- its just how she feels about the situation. So, the most important thing to do -- especially since she is so young -- is to try to address her insecurity. For this, because she is so young, I would contact your pediatrician for advice.
I agree that making it clear that her behavior will not result in your husband not being affectionate towards you -- she just in general has to learn that negative behavior does not produce positive results. But at the same time, I think it makes sense to try to understand her insecurity and how she is reflecting it, and make efforts (again-- I think the pediatrician is a good place to start on what these efforts should be) to reduce her insecurity.
This is kind of bizarre. If you are her mother, I think your husband needs to make this VERY clear, in no uncertain terms, that you are his wife and she is his daughter. This is the time for him to step up and make it clear you are his partner and she is the child.