I'm an INTP female.
Never dated an ENFJ, but my sister and best friend are. I REALLY love my sister and friend, but I don't think an ENFJ and I would be a good match (sorry!). I think I'm a good sideline friend for the ENFJ's in my life, but I doubt I'd be a good focus for their energy.
I think some other INTPs have mentioned this, but you really, really need to talk it out w/ her.
Here's how I would talk to an INTP about this: Tell her that you are jealous, that you don't want to feel jealous/inferior to her EX, and ask her to change her behavior (if she's like me, then SHE needs you to lay it out real simple like I just did). Be absolutely calm and not dramatic when you explain it to her. Don't exaggerate or throw emotion around. After you explain how you feel, it would be best if you give her time to think about it. If she agrees to make some changes b/c of how you feel, you're good and she'll probably stick to it. If she refuses, the relationship's probably not going anywhere either b/c she's immature or she doesn't like you more than the ex (after all, you seem to be asking for something that's totally reasonable and she should realize that if you explain it and ask her to think about it).
As an ENFJ, I'd caution you to be careful trying to motivate an INTP toward something you want them to do. If INTPs senses you're manipulating them, they respond by doing the exact opposite of whatever it is they think you want them to do (she might be doing this already from what you describe). Your best bet w/ an INTPs is to reason and talk it out with them. I think most INTPs want you deal with them by reasoning with them. They prefer talking it out to having you figure out what motivates their passions and desires and motivate them in a way that's compatible w/ what you want.