Not at all...press on. By playing more than one instrument, it actually makes the playing/learning of each instrument easier..because the musical concepts are the same,and hence strengthen the development of musicality. There are several superb multi-instrumentalists out there, some even virtuosos in more than one..which the purists would argue is hard to accomplish, but we're not thinking of virtuosity now, are we? You just would be interested in your daughter's musical development.
Piano is the cornerstone instrument, and many good jazz/classical and even some rock players start with this no matter what their other chosen "axe" is. That way, you can compose, arrange etc...for any instrument just by going back to the keyboard. Now guitar and piano work very well together, and there are a couple of sax players that are guitar players as well (I play both, and bass also...). Sax is got it's own thing because of the breathing, embouchure etc...but you 'd be amazed at the number of people who play many instruments well.
Some examples:
Jack DeJohnette : world class jazz drummer, is also a virtuoso pianist, and I think plays some other things.
Ralph Towner: "the" acoustic guitar player, for sure, but started with piano, and often will do piano gigs. He actually is superb on many instruments including English Horn..etc..He is a wizard, though.
Jaco Pastorius: known for the electric bass. But he was a fine drummer, and excellent pianist.
Keith Jarrett: of course known for piano, but I heard he was a superb guitarist as well.
The list goes on. I do recommend and encourage your daughter to do guitar as well, and to start with an acoustic, rather than electric instrument. This will enable her to really learn to play, instead of getting lost in the effects, and power of the electronic instrument. She could then grab an electric later.
Try acoustics by Yamaha; their price range varies, but anything in the 175-250$ range by them should be excellent value. Very sweet sound. I'm talking steel string here. Nylons are trickier, because most of the cheaper ones sound terrible. A reasonable classical nylon would START at around 250$...Try Harmony or similar brand. The good nylons...sky is the limit.
Other brands to consider, that are relatively inexpensive and sound great include:
Tacoma (made in Pacific NW), they do have lower price ranges on some models, and fabulous sound.
Fender : actually has some acoustics at intro price levels that are not bad.
Martin (Shenandoah): this is their lowest end, but still fine guitars. Their regular line is very expensive, but I still think the best of the dreadnought variety.
Bottom line: check with your local music store, and tell the salesperson, that your daughter is interested in starting guitar, that you want decent sound,and a well built-enough instrument,that won't cause her to feel frustrated and quit.
Any other questions, let me know. I personally feel..the more instruments, the better..but of course most musicians find they end up playing one foremost over the others.
Good Luck,
Gene
