i assume this is a 'candid' moment kind of thing, rather than a posed picture? if it's the latter, patch17 has suggested some pointers on how to get a stronger composition and technical considerations to look out for. i feel they are worth considering which may help bring out the message (of course, it's your call how you interpret and apply)
*OT* although the part about capturing the "reflection of the phone backlight in her eyes" may be a bit tough :sweat: the overall ambient overpowers the backlight by alot, i assume. a good example...take out your own mobilephone in similar lighting conditions and see if the backlight is readily seen. but it's a good idea anyway~ */OT*
as a 'candid' shot, the part which patch17 suggested about moving around and shoot,shoot,shoot might not work. in fact, it might not work at all if you are going for capturing her spontaneous expressions and reactions to the phone. if i were her, i would go 'W T F' ;p
in this instance, capturing the 'feeling' of the moment is a more important consideration over the rest. at this moment in time, i do not have what it takes to tell u how it works. but i can suggest looking more and studying more about pictures which work for you. try to see what is it about the picture that works for you, and how the photographer go about doing it. build up your own library of 'feelings' and apply it your way.
like patch suggested, if you are on digital..shoot,shoot,shoot (if only i practice what i suggested T_T ) however, do consider this....shooting more, means the chances of getting more booboo shots goes higher too. don't let it become a case of randomly choosing a few good shots out of a ton of so-so ones. be aware of what you are doing and what your possible mistakes are.
:sweat: i'm actually talking more about myself :embrass: