Okay, I think I understand the situation a little better. You seem to be concerned that maybe someday your husband will leave you in order to be with her more. That fear is driving what seems to be an intense jealousy. Is there anything else that might be making you feel jealous, or does that about cover it?
"And to test him, I have tried to shut him out, push him away, offer to leave, but the harder I push him away, the more he comes back; I guess if he wanted her bad enough, he would take me up on those offers, wouldn't he?"
Yes, I think so. Surely it is enough to test him a little, and then take him at his word? Can you trust him? Do you trust him? Has he ever done anything to weaken your trust in him? Do you have any grief or trauma that you experienced in your past that might be hurting your ability to trust now?
How intense/extensive is this jealousy that you feel? Can you live with your husband spending some time with her, as long as he doesn't leave you?
I remember the first (so far only) time I went on this one really bad-ass ride at Cedar Point, the Top Thrill Dragster. It shot straight up in the air, and went straight back down, and we are talking a *long*
ways up. When I was in the ride, I was just clutching the safety restraint, eyes squeezed shut, hanging on for dear life. This image came back to me when I read about your situation. You seem to be caught in some kind of terrifying ride, and are clutching on to your husband for fear of losing him. Can you loosen your grip just a little, or is the terror too intense?
I am just curious to know what is driving these intense fears you are experiencing. I respect your right to not talk about it, if you don't want to talk about it any further. But if you change your mind and do want to talk about it, I'm listening.
Take some comfort from your husband's reassurances if you can. Sometimes the fear of vulnerability is all it takes to throw us into a defensive posture.
Hope this somehow helps,