I think that if you continue to do it recreationally now, you could simply describe to her one or two of the fun nights you have over the course of the next while. If it seems appealing to her, she'll want to know more. I had been doing M for a couple of months when I met my partner (now of 5 years). He had been very anti-drug when we met, because of the horror stories out there. One night some friends and I were going to do it and he said he would be okay hanging out with us when we were high, so as we were dropping that night I let him know that we had extra if he was interested at any point. After knowing I had been doing it for a while and it hadn't ruined my life/hospitalized me, I guess he felt more comfortable and he ended up rolling with us that night. We now roll together every month or two, just the two of us or with friends, and he loves it as much as I do!
I think the key here is that the partner needs to see that drugs do NOT always ruin lives, and do not send you to the hospital or to prison if you use reasonably infrequently. My view before I started taking drugs recreationally was that you will become an addict your first time using. After I had seen many of my friends start using different drugs just occasionally, I recognized that you can actually take drugs sometimes and still have a normal happy life! Be an example to her. If you start taking MDMA again with friends, don't say anything to her but let her see. You can role model responsible MDMA use.
After a while, maybe after you've used it a few more times, have a heart to heart to her and explain why you want to share that experience with her. Explain what it does for you, the precautions you take to stay safe, and what you think the benefits would be. If she is not comfortable with it after that, let it go and don't bring it up again unless she does. There's a difference between pressuring her and gently letting her know how you feel and what your experiences have been. The difference is that sharing your thoughts only needs to be done once in a complete, honest and loving way- after that if you bring it up again it moves into more of a pressuring thing.
Some people need a while to ease into things. Some other people genuinely have no interest, and that's okay too. Rolling together would be the cherry on the sundae in a good relationship like yours, such a treat and a beautiful extra but the sundae is still wonderful without it
A note about her anxiety disorder: There is anecdotal evidence on BL that MDMA can trigger panic attacks, but there is also anecdotal evidence that it can help with anxiety disorders. Explore this site
http://www.maps.org/research/mdma/. It's a great website about using M in therapy, it's possible that in a safe and therapeutic context such as at home with someone she trusts, it will be a very positive and wonderful experience for her!!