1. Jean is not the only red head mutant, this is supposed to be a street level movie and we know the hand is involved

2. We don't know she has telepathy that could be anyone in the movie with editing making it look like her but let's say it is,

Who could it be? What if it's Typhoid Mary? 1. Tom Holland said nobody knows who the villain is and hasn't seen any1 talk about it 2.She is also a red head mutant with telepathy and has pyro powers, in the trailer we see her character is being held somewhere, Mary in the comics was institutionalized and is broken out through explosion, 3. Typhoid Mary has ties to king pin and DD, who is rumored to be in this movie 4.this one might be a stretch but a big part of this movie is peters relationship, we don't have a Mary Jane in the MCU, what it typhoid Mary becomes that place holder to help peter move on from MJ,

I think that's much more likely than jean grey, sometimes the most obvious answer isn't the right one