Fox makes one pair of women's boots, but I can't recommend them--they are their lower-end boot, the Tracker. I had a pair of trackers once--not the women's ones, this was before that--and they were uncomfortable and ended up falling apart. Now these new ones might be better, but that was my experience. I would look at Alpinestars for starters--they make a size 5, which is lower than a lot of the other companies go. Maybe think about the Vector since they are a little bit shorter than the Tech 6 or Tech 8. I have a pair of Sidi Force boots, and I really like them. I'd figure just one size smaller than her women's size rather than two--I wear a 7.5 or 8 in women's shoes but my boots are a size 7, and they fit fine. I suppose they could be more snug, but that was the smallest size and I don't get blisters or anything. Also try a thick sock like the MSR hi-bulk socks.
As for pants, most of the brands that I have tried run pretty true to size except for the MSR. If she is an 11/12, then she should try a 10. The other brands I would get her normal size. I have not tried on the Answer or Thor but I have had O'Neal, Fox and Acerbis women's gear. The Acerbis is by far my favorite, but the only color it comes in now is pink, so if she's not a pink person, I wouldn't go that route. You can still find the old colors in blue/white/red in back stock on sites like
www.mxsouth.com or
www.motorcycle-superstore.com. Companies which make women's gear are Answer, Acerbis, O'Neal, MSR, Fox, Thor, LBZ (not my favorite at all) and some one-off companies like
www.vixenoffroad.com and
www.sickracinggear.com.
Good luck!
PS--it might be easier to TAKE her shopping than try to surprise her. Then she can pick out exactly what size, brand and color she likes. She also might prefer a non-women's company; the fit might be a little different, but there are a lot more choices in color.