Give her the information and let her decide for herself. Erowid is a great place to start.
I find that it's very hard to have a bad time on MDMA provided that it's good quality and a reasonable dose. There's definitely potential for psychological progress when it's used in a therapeutic setting, and might help you connect or work through relationship issues. Whatever she decides, don't coerce her or guilt her into doing it. I strongly suggest she reads up on the effects and risks so she knows what she's getting into, which is a good idea with any drug.