we have a lady in the office whose perfume is causing some major problems... how do we tell her to take it easy on the fragrances without offending her?

Tell it to her in private. Say something like, "I need to say something to you and I want you to know that I'm telling you this because I like you and I respect you as a coworker. Perhaps you haven't noticed but your perfume/cologne is too strong for many of the others who work here. They didn't want to say anything because they didn't want to hurt your feelings, but I felt you would want to know. Your perfume is fine, but you put on a bit too much. I'm sorry if this hurts your feelings, but I know you wouldn't want to intentionally wear too much perfume."

Perhaps her sense of smell isn't that good and she doesn't know she's so overpowering. Maybe she's been wearing that brand of cologne/perfume for so long she's lost sensitivity to it. Good luck.

tell her some peopel are very sensitive to smells and its affecting their allergies with the overdose of perfume. i hate when people do that!

you can say that someone is allargic to the perfume, and start snizzing once in a a while.
or you can certainly say it as a joke and she will understand it on her own.
good luck