[EdwardSinclair]

I've been in the same boat before, and it didn't end up nicely!
It all depends on the person, I suppose!
I would be very careful though, and one way you could do this is to introduce the subject slowly and only if you know she is going to be comfortable with it!

----------------------- Tips:

First you have to both be able to watch porn together comfortably.

Secondly she must be interested in finding out about what a guy gets out from anal pleasure, e.g prostate stimulation etc...

Thirdly once you have established the ground and both of you are comfortable with watching porn together, show her a clip of a guy and a tgirl and ask her what she thinks about it... get some feedback and assess if she's ok with it, and whether you can relay more information about the subject.

If you succeed it will open up a whole new world for you both during sex (strap ons/butt plugs play)!!

If you fail, this is the type of thing that could end the relationship, especially if she suffers from low self-esteem, as she may feel insecure! It all depends on how you approach her with this, and her predisposition to be open minded with this!