Cut out the rot. It’s the only answer. I’m sorry but radical homosexual behavior requires artificial new hosts since there is no natural method of spreading. Push them out. It’s no different than amputation of gangrene limb.
The bio mother and her consort should realize that if they have her enrolled in a Catholic school, she has a right to be taught Catholic doctrine, including that marriage consists on one man and one woman only.
And the "lesbian moms" should not expect to be accommodated in their couple-hood. One is the mom; the other is basically no relation that can be recognized by the Church or the Catholic School.
If they are offended by this and want to pull the little girl out of the school, then that's on their conscience. We should neither reject, not spotlight, or isolate her. And as a baptised Catholic in communion with Christ, the little girls has a right to true Catholic instruction and the sacramental life. Inasmuch as that is up to us, that is what we should do.
All this gets changed quick if the "lesbian moms" talk or act in a challenging way to turn this into a confrontation.
It's a tough situation, because the little girls has the right not only to participate in the Church, but also to be raised in a Catholic home. But that part is beyond our control.