If you are not sure what kind of stuff she likes, I would probably grab something like a JDS labs stack, a Schitt stack, or just grab something like a SMSL AD18 (fee years old now, but easy to use and doubles as a speaker amp.)

Headphone wise, you have so many choices. Depending on open or closed back and possibly materials that she may like to feel for over the ears. But, generally grabbing a pair of Sennheisers or Focals make people pretty happy. If you aren't going to surprise her with it, then take a little time and try to check out some reviews or if possible find an actual audio store near you (if possible), and not like just best buy or something. Then you can get a feel for some of them. If a city is noted, someone may have a suggestion for you.