You are right about UCCB not counting towards gross income. Whilst job loses including dropping temporary part time jobs to boost income to meet LICO may contribute to PGP rejection, MAT leave could be argued under certain circumstances. The main reason for setting LICO is to ensure that the sponsor has enough income to support the parents and grandparents, which reduces the chance of having new comers relying on government support. As for REMM's case, she would have met LICO had she not taken MAT leave or taken shorter MAT leave. Once she's back to work again, she will meet LICO; hence, she can support her parents. Some applicants sponsor their parents mainly because they are having a baby and want their children to grow up with grandparents. If having a child ended up being the cause for rejection, I would definitely appeal under H&C grounds. It's not as if she stopped working those part time temporary income boosting jobs or lost her job altogether.
In any case, all you can do is hope for the best and prepare for the worst. There's nothing you can do now. If you have a co-signer, then you could be in the clear too.