More generally speaking towards your situation, it's hard to demonstrate this online because we cannot see or know the people involved. However, you may want to get to know this girl more first before taking MDMA with her if you've only had a "few hang outs". That's personally speaking though if it were to be in a chill 1-on-1 hang out situation, you don't want to build a false relationship created by the MDMA that turns out to be unreal. If you're going to party or rave with a newcomer then it might seem more worthwhile.
What are your reasons for wanting to do MDMA with her? What setting would you take it in?
Everybody I have had taken MDMA with me were always people I knew very well, had known for a long time, and actually knew deep down there were really solid people. That's why taking MDMA with real friends is so special, because those things that go unsaid are finally spoken, and after the experience you realize the significance. Ever wonder "what if I never rolled with so and so, man our friendship would be so different and not as good"??
Back to topic.. Speed is something people are going to become addicted to more than MDMA. If you don't know the girl very well I'd make sure mentioning that to her wouldn't freak her out, though it sounds like she's down for drugs.
On a side note, I will just state that the only bad drug experience I have had was by taking an SSRI (Paxil). The SSRI derailed and ruined my life for the time I had taken it (8 months), and it took me two years afterwards to get back to the person I was originally. I'm not your doctor, but if you haven't taken into serious consideration the risks of SSRIs that your doctor isn't going to tell you, I would really recommend doing extensive research before deciding to take this medication. If you're hooking up with girls which it sounds like, your anxiety can't be that bad right?