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The LW has already been with the guy for years, and in less than two more years the kid will be at the age of majority. Then they can just move her out to her own pad and let her figure out her own place in the world (sounds like daddy can afford to support her financially).
The daughter could continue with an adult version of the spoiled, pampered life she's accustomed to. The father would finally be rid of such a burdonsome person (just cut a check once a month, and go on with his life). And the LW can finally score the rich guy without the bother of the brat from the previous marriage (ka-ching!).
Just use a little patience folks, and everything will work out just fine.