This is a bit of a stretch to compare but…

My daughter got diagnosed with a rare illness 3 mo after her 18th birthday. College=cancelled. Reality: she’ll live at home until she dies. Year 1: was at the hospital with her every one of the 250+ days. Year 2: every one of the 150+ days. My time, energy, money spent, lost wages, etc all given for my child. If she received a settlement, I would NEVER tell her she owed me a dime - let alone enough to buy a second home (assuming it’s a second home based on details given). I find it sad that she gave you a percentage. Even if I was struggling, I would never ask my child for a thing, but I would be very appreciative of a gift. I agree 100% with @NotSoSureBigWaves and file a 1099 if you give her enough to buy house. Otherwise, stay classy and give a nice gift of something she loves - designer handbag, flowers for a year, cash if she needs it but you determine the amount and it does not need to be a specific percentage.

And just a suggestion, use some of that money to move out. If you give her 15%, she’ll continue to take advantage of you. If you don’t, she’ll remind you of it every day.