Junk the seat and invest some money in a good one.

Like HM said, you can find a wider, more comfortable chair. There are models made for women. Some have gel pads built in. Covers do move around and will cause more problems than they solve.

DO NOT LET A BIKE SALESMAN talk you into the 'top of the line' model, if you can, sit on a few to see how they feel.

Plus, the type of bike has a lot to do with the seat.
The lower the handlebars, the farther forward you will lean and have less contact with the seat.

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Padded bike pants are great too. Long legged, cotton undies are the best to wear underneath. Drop some baby powder into them and you'll stay comfortable.

I rode to work for a long time and suffered from more crazy stuff related to bike seats and pants that you can imagine.