Calculate how much you will end up paying total in each case, and compare. The "end" here is when you have both paid off the high-interest debt and payed down the mortgage to PMI removal.
The numbers you want to look for are:
- how much did you pay in interest on the loans by the time they were paid off?
- how much did you pay for PMI by the time it was removed?
- how much interest did you pay on your mortgage by the time PMI was removed and the loans were paid off?
- how much do you still owe on your mortgage once PMI is removed and the loans are paid off?
You can work out these numbers assuming no windfall to get a baseline of what you'd be paying anyway. Then re-asses with the windfall applied to either the loans, the mortgage, or split between both. Whichever approach minimizes money lost to interest and PMI payments is likely your best option.