Cranks are either double or triple, i.e. two or three chainrings. You can buy a standard double with a 39 and 53 tooth chainrings, or a "compact" which makes the little ring a 34 or so and the large ring about a 50, which has the net effect of adding a couple teeth to your rear sprocket.<br><br>
What I like about the compact for many riders is you can have a low gear to climb hills, but still keep a fairly tight gearing, for example if your old bike had a standard double and a 12-25 cogset in the back (I'm guessing) then you could go with a compact and a tighter 11-23 in the back and still have exactly (more or less) the same hill climbing gear, while losing some of the two-tooth jumps (i.e. the 17 to 15 we all hate) on your old bike.<br><br>
I realize it sounds confusing, but having the "right" gear on your bike so you can turn the "right" rpms while keeping your heart beating at the "right" place is really a plus and the compact will help this.<br><br>
If it were me, I'd count the number of teeth on the largest cog of the rear of your present bike and look for the stamping on the small chainring to identify the number of teetch (39 usually) think if it worked out for you and speak with the shop about replicating this present gearing but with a compact and how that might impact the cost of the bike. Just a thought, I really do endorse compacts for most women of average fitness as a win-win solution.