So many, many choices to choose from. My first suggestion would be to take her to a local shop or CC/BB to listen and figure out which brand/type of speakers suit her personal tastes. Everyone's ears are different.
Personally, I'd probably buy some generally inexpensive speakers and use a modest external amp to power them. In most cases, they'll sound better than high end speakers powered by that Sony HU.
I might get some speakers like this for the ease of drop-in installation:
[img]
http://store6.yimg.com/I/competitiondirect_1657_57922737[/img]
[img]
http://store6.yimg.com/I/competitiondirect_1657_58004956[/img]
Then, I'd use a modest 4ch amp like this Pioneer GMX554 (50x4) to power them:
[img]
http://store6.yimg.com/I/competitiondirect_1657_43827549[/img]
My total budget would consist of:
Audiobahn 4x6 component plates - $37
Audiobahn 6x9 triaxials - $54
Pioneer 50x4 amp - $146
8GA amp installation kit - $15
Grand Total = $252 (from competitionsound.com)
