Hi, my 12 year old daughter plays a black nickel Jupiter tenor sax. It has beautiful intonation and a nice dark sound; and the quality is great. A little bit cheaper than the Yamahas and well worth looking into. Her best friend plays a rather beautiful Yanagisawa which I think sounds better, but a Yanagisawa will always cost more.
May I suggest that you have a browse thru Goldcoast Brass and Woodwind's website
http://www.gcbw.com.au/
they have both Yamaha and Jupiter abd Yanagisawa alto's (new and used) at some of the best prices around and will ship to you at very reasonable rates. It may be best to take your granddaughter to a music shop and let her try the instruments for herself - she will know which one she likes the sound and feel of the best. It is also worth having a look at / try with different mouthpieces to the one that comes standard with an instrument - there may be one that suits the shape of her mouth better and be more comfortable.
Cheers Kerrie