Well, there's a difference between just reading the content of threads and "impersonating" the handle. She can read any thread in printout format, if OP so provides to her, without rendering his own FT password. With FT P/W, she can certainly do more than just read.

With OP's FT P/W, she could act like OP in FT and do whatever she wanted (posting, ridiculing, or even inflaming) under OP's identity. She could even get OP into trouble. (I am not saying she would.) But what if she had a post that got OP suspended? Could OP claim FT identity theft? That's why I thought of all the TOS complications.

I didn't mean to go OT with my line of "philosophical" discussion. To OP, sorry I didn't mean to question your trust and relationship with your GF. Nor was I challenging her personality. Those "technical challenges" just came to my mind when I thought about any acceptable workaround.