Assumption #1 – everything is contrived. Having said that, it is totally weird that she would be sent by herself from wherever (does their mom live in Salem?) without the mom calling Rafe or his sister. And since we know she is not a short term actress, why will she end up staying there with them? I know! The mom needs to stay with the grandmother to take care of her so Gabi will have to stay with her brother and sister and go to Salem High. And, of course, she will fall for Will which is totally weird since her brother is living with Will’s mom.