First off, don't listen to an M2 about stethoscopes, he is behind your daughter. I would get a littmann classic II se http://www.amazon.com/gp/aw/d/B000F4UOWK/ref=mp_s_a_1_10?qid=1387373249&sr=8-10&pi=AC_SX110_SY165_QL70

There are other cheaper brands, but frankly people like to have littmanns, it's almost like having a pair of nikes, silly, but will make her happy. You can get the II for about 50$ if you shop around.

Edit: also just tell her how proud of how hard she is working for her goals, it means the world and med school gets miserable and can feel suffocating :)