The mountain bikes in that price range aren't usually women's specific in the same ways that higher end bikes are. The less expensive bikes all have comfortable seats, low top tubes and rise bars. Some are offered in a classic "ladies frame" with a step over top tube.
If you were willing to pony up a couple hundred more you can get this. Entry level Trek
820 WSD - Women's - Trek Bicycle
when comparing a bike like this to a piece of **** Walmart special be sure to keep in mind resale value and SAFETY! A name brand bike purchased a real bike shop will be assembled by a qualified bicycle mechanic and will be the correct size. Add to that the fact that the shop will spend a little time making small adjustments during the sale that make a BIG difference in comfort. For example, seat height and angle, the position and height of the stem, bars, brake levers and shifters. These are little things that could make the difference on weather or not your wife actually rides the bike. Anyone is more likely to actually ride a bike that shifts well, brakes safely and easily and is comfortable to ride. Also, you will have the support of a bike shop during ownership. A free check over and a quick tune every year is essential. (At my shop we give free lifetime tune ups with every bike we sell and yes, I do the same exact tune that normally cost $70). Not all bike shops are created equal so be sure to not just find the best deal but also a shop that treats you with respect and gives you attention no matter how much you are spending.
I guess I just hate hearing the "go to Walmart" thing. Those bikes are the equivalent of booty fab steering on a clapped out rig. I see it all the time and ALL those bikes are sketchy at best.
I can guarantee she will only ride the Wallmart/Target bike a couple of times and hate it. Rant over - Good luck
