I am assuming that since you have left her a review already you have seen each other and at least established some form of trust with each other and generally get along, i mean there is always the chance that you guys wont get along or something bad will happen but i think life is all about taking risks and trying new things so i would tottally say go for it and ask her.I think traveling with someone (ecspecially someone your attracted too) is always funer than traveling alone!Hope you have a great trip in europe!!
                 xoxo Lilly Lockhart

No matter how good their shoes look, many ladies have holes in their socks - you can't see their problems - on a long trip it might be revealed and you are a long way from home.

On the other hand, gals will complain about the dudes who wear fake chains, save to make it rain, stunt in a car they cant afford and still look for a gal to keep it real.

Goes both ways.

Keep it real.  The key is trust.

It can be very enjoyable and a great way to play out some fantasies along the way.

Key advice is to plan your outs, mutually!  Don't assume that only you may want out of the extended date/trip.  Plan of x of y days with option to extend at the pre-defined rate and cost of ticket change.  Likewise agree to same method if she desires to opt out, she gets paid the days accompanied instead of days agreed and she pays ticket change.  Offer her the option of personal days along the way such as a 7 day trip with 5 days with you and 2 for her to go do what ever which is great if you have preplanned business events.  

Discuss it openly and you could wind up having the time of your life!

I would put a LOT of thought into this first.

I have done several short trips with providers that I have known over the years and enjoyed most of them, I also took a ten day trip to Hawaii with a provider friend that had turned into a GF, it was a fucking disaster, we broke up immediately after returning.

Provider or civvie, three weeks is a very long time to be with anybody.