Basically, both phones will meet your 3 demands so I
guess your only problem is Android vs Windows. There
is probably no definitive answer as everyone is different
so I don't think it matters, just get the one she likes the best.
As for the Android vs Windows question:
Choosing between these two great operating systems isn't an easy task, as we've discussed they're both great performers, with a myriad of virtues to keep you up to date, entertained and in control of your daily life. Where the divides do occur they're minor, leading us to happily endorse either of these great pieces of software.
The best way of deciding which platform is right for you, is to weigh up your personality and demands. If you're a techy person, who wants to milk more out of their smartphone, customise it and generally push it beyond its out of the box state, then Android is the one for you.
But if you're keen to pick up your new device and utilise it to its full potential with minimal fuss, you'd be best advised to look at Windows Phone 7. One thing's for sure though, whichever one you choose you're in for a fun time.