"Gina's been with Mamma Mia! for years now, I highly doubt something abruptly happened. She probably thought she'd stay, and then realized it was a very different experience with the whole new cast? Could be as easy as that..."
So because she's been with Mamma Mia for years, you doubt something abrupt could happen? Like I said, she could have had a health issue we don't know about (and that is none of our business). Or a family emergency that requires her extended absence.
"We like to snark around here. Sometimes we actually talk about theater...but we try not to let that get in our way." - dramamama611