This is a common side effect unfortunately. Many women find the issue is lessened or resolved after being on the meds for an extended period of time (greater than 3 months). However....If it is effecting your libido, and sexual gratification, that can be depressing in and of itself.
There are other antidepressants out there, that don't have that effect, and are old, and have been around forever. Elavil or amitryptilline being the first one that comes to mind.
If she is not reaching her climax in traditional methods, you should certainly consider other methods, like Sam says. However if she still can't then call the Dr.