nah she was definitely roly poly but kids out grow that. I agree that she looked much older than 4 (Gabby would still need 10 months to have that baby) Maybe she and Carlos finally adopted.. or maybe she and Carlos are no longer together and those are her 2nd? 3rd? husband's children.
The girls were obviously upstairs alone so Gabby could be single, the father could have been at work or Carlos just can't see what they are up to. It will be fun to watch! I think Gabby's is the only storyline I'm looking forward to.