Whenever she wants, however she wants?
As someone in her position, or at least dating a guy with kids, I definitely get interrupted by the kids. Whether we're out, and something happens to one of the kids, so he gets called home early. Or if I'm at his place, and the kids are around (we've more or less given up on trying anything while they're home, though). Also, if I couldn't text him while he was with family, I would be severely limited in my time with him. He's on his phone, anyway, might as well be with me
Kids puts restrictions on ALL parties involved with the family, pre-established or becoming established.