We’re going back a lot of years here, but . . .
My interpretation was always that the parents had hired her to help their daughter, and never expected her to risk CA on behalf of those other lost souls. Tangina takes the risk that she can lure CA near enough the light to release the others, while her Father’s disciplinarian demand will be strong enough to keep her from walking through.
It was a big risk to take, but Tangina doesn’t see CA going through to the light as a huge tragedy - only being lost between the worlds is horrible to her. Ther parents, understandably, would see her crossing over too soon as a circumstance to be avoided. . .
So when Tangina gets sort of steely, and seems to be ignoring all external input, I thought it was just her putting her own part of the plan into action, knowing the S would hit the fan if it didn’t work.