Progressive breeding program without an unrelated, adult bull?! And apparently without plans to bring on in? Renee has been all alone without female company for way too many years. And she could have had one more calf in the meantime if she had been moved to a zoo with an adult breeding bull, as she should have.
Twiggy is definately too old for a sucessful first pregnancy. Given her bad shape due to neglect of her former owner (very small, underweight for an adult female elephant) I very much doubt she is even cycling. But even if she does, at her age, she`ll likely never get pregnant, and if you mircously does, she has no chance to give birth to a life calf. They are delusional if they really think they can breed with her.