The Lane 1 XXXL would likely be the perfect ball for her. It is expensive as far as plastic/poylester balls go, but it also has a fairly agressive core, aimed at going long and breaking late.
If your girlfriend (if my girlfriend bowled 176, she would be my wife, btw) has the typical dainty chick realase( she kinda drops it and waves her hands, hoping the bowl will magically hook that way) then the XXXL would be a complete waste of money, because her speed would be so low it would likely hook into the gutter.
If she can throw some revs off her hand, the XXXL will skid/slide into the clean and make a late break, probably inches from the pins, giving her a better hit. However, I don't think Lane 1 offers balls less then 14 pounds, though I could be wrong, that may be a problem.