What does a mixes audience mean? Mixes dancing, featuring Lipa? Which organization has any reason to hire Lipa to provide the music for their mixed dancing?
I assume that you mean either a mixed concert, which lets be honest, is perfectly fine to any adult who’s ever been to a frum concert; or weddings that have mixed dancing (but among those baalei simcha, the majority probably at least start with separate dancing.) Neither of those is that big a deal, especially not from the perspective of the performer. Even if he once decided to refrain from singing at mixed concerts.