could i make a free trial account and invite an alt on a low pop pve server so i can get phased in maybe that would work

no, you get phased to the realm of the higher level character now

really ???
what if both the ppl are 90 tho bc sarah was 90 and i was 90 but i got sent to emerald dream ??

idk this cross realm shit is confusing 

Then its the realm of the group leader.