Presumably because she never met anyone worth the hassle?
Look, I'm not arguing Fel is a starry eyed romantic just waiting for a prince and his ten inch horse to ride in and carry her away to a happily ever after forever in castle Bumfuck. I was arguing against the notion that she's driven by lust and therefore not capable of, or willing to engage in, romantic love. She enjoys sex, she uses it as a tool, but she isn't governed by it.
I's also like to point out Fel doesn't actually have money. Her husband has money. She has access, as his discretion, to certain limited benefits derived from his wealth. She herself likely owns practically nothing, if a prenup is in play, which there probably is.