I know it will happen simply bc I don't want it to, aside from a loved one dying, what could bring more widespread drama than Summer's return...
my theorycraft:
at this point Nami and Bella will make a temporary alliance realizing they cannot allow summer to re traumatize him/ take him away, they'll plot
to murder her and hide the body after they've chopped it up into tiny pieces
or more likely to keep her away from MC & eventually they'll get to know eachother & end up as actual friends, see how easily our dream girls can be friends & eventual lovers *Drooling on himself at this point*