The one big risk, as you know, is that if you have any conflict with her either work-wise or academically, it's probably going to spill over into the other part. But that's not gonna happen, right?
The plus side is that if you were really busy or stressed out at school, she might be inclined to cut you a teeny bit of slack at work, or vice versa. Or at least be flexible about times and so forth.
Would you feel comfortable talking to your MSN advisor about it? Or anyone else at school? Even if they're friends/colleagues of this woman, someone ought to be able to understand that you feel apprehensive about possible conflicts (and putting all your eggs in one basket, as it were) and give you some reassurance.
I don't think there's a right or wrong answer here. You're probably going to have to make a judgement call. If you are getting a good vibe from this woman and she seems friendly and flexible, I'd say take it.