Well, it sounds like she isn't leaving much room for you (separated, but with a boyfriend?!?), so that makes me think she's hoping that if she hangs on and rubs the OM in your face enough, she can drive you to the D (and then probably blame you for leaving her!). Sadly, it's not unheard of.
Of course, you have to decide what you want/need to do, but if it were me, I wouldn't give her the satisfaction. Like I said before, I'd do the legal separation so that everyone has their own things, credit, debts, etc. and she can't drag you down financially.
Then, wait her out. If you're like most of the LBS' around here (myself included), you'll have plenty of baggage to deal with before you'll be ready for someone else and that'll take time to work through. In the meantime, she'll likely get bored pretending to be the suave European with a husband and a thing on the side.
She may discover you're not as bad as she thought, she may really find someone else she'll want to be in a serious relationship with (in which case your M will become a liability), or...and this is the most likely...she'll come to recognize that when you're married and looking around, the only people you tend to attract are users, sleaze bags, bums, and other married people looking for a roll in the hay without strings.
At that point, she'll either want to work on it or get the D herself. In the meantime, if you've been living your own life separate from her, you'll be in a good position to let her go (you'll have essentially done that by then anyway) or know what you need from, and can give to, any rekindled relationship.
