I do some paper crafting, and occasionally use water color pencils. (I.e. I am NOT an artist...)
I like Staedtler Karat Aquarell Watercolor Pencils, they make a nice set, and pretty reasonably priced. I think you can buy sets at Michael's (i.e. use a coupon!).
Faber Castell is also a nice brand for water color pencils. An art store near me has them individually - if I need a specific color.
One thing I would highly, highly recommend is to get a really, really nice pencil sharpener. (An "art" store will have these.) They really are in the $3-$5 range, but it makes a HUGE difference in what she is doing. A regular pencil sharpener will not cut it.
Also - don't feel like you need to get a big 120-pencil set. One of the fun things with water colors is the ability to blend and make other colors. a 12 or 24 set will probably be more than adequate.
I would also get her a tablet or some big sheets of water color paper. And, get some water color brushes too! (Again - micheals has a whole section - use a coupon!!)
Sounds like a GREAT present!!!!
(Sorry - I can't help with the "regular color pencils" just haven't mastered that medium)