I agree with Doubty.
No, don't do that! Doubty
sucks and is boring
you're just jealous
Well, since you have pretty much decided your strategy, how about asking her to paint a portrait of you? That way she'd feel a bit less obliged and under pressure. And it'd at least add a remotely romantic touch to the whole affair.
You could offer to buy all the necessary ingredients (paints, canvas, brushes, paint thinner, etc) for her and ask her to give you a wishlist/shopping list. Ths way you could be certain to buy exactly what she wants.
Be warned, though: painting materials are quite expensive, particularly if she prefers oil painting ( I do that myself - you wouldn't believe the prices! 10 bucks for a 3 tablespoon tube of lead white!). It quickly sums up to $150-200 only for the materials for 1 picture.
You're lucky if she prefers watercolours - they are a good deal cheaper. Still you'd have to spend about $80 for the basics. If you go for the really good brushes, you can easily spend $20 on one.
You'd propably be cheaper off if you'd invite her to a really exclusive exhibition and dinner. And maybe she'd like that even better.
How about going to the 555 arts exhibition? (Every Wednesday from 13:00) http://www.555arts.org/event-calender/
for general info have a look at http://www.555arts.org/history/
Modern, young, fresh and avantgarde art all thrown together - this might be just the thing to inspire her and in this huge choice she is sure to find something she likes.
Or how about something classical: the Rembrandt exhibition? http://www.dia.org/calendar/exhibition.aspx?id=2306
By looking at someone else's paintings a painter can learn a lot about the painting technique used by the artist. And when does a normal person get a chance to see a Rembrandt up close?