No, I didn't find a marriage, but not knowing the forenames for a common name like Clark(e) makes it very difficult, especially if Frances used one of her other forenames. That's why I thought the census might be easier, because of the b.IOM.
I wouldn't be too concerned about the spelling of Clark(e), which would depend on the vicar or clerk who recorded her second marriage in the IOM, or how accurate the person was who re-transcribed it. I think I read somewhere that Clarke was the usual English spelling, and Clark the Scottish? (But could be wrong.)

Sue