If Mabel had to choose between Gideon o Jeff who do tu think she would choose

I think it should be...

Gideon

I think she should choose Gideon cuz hes actually human!

I really don't think she'd choose either. To her credit, Mabel's not one to lie down and take such unprogressive choices.

She'd dramatically exclaim something to the effect of, "I would rather DIE than have my hand forced into date-lock!" before comedically attempting to kill herself, and then Dipper would hastily tell her not to be so drastic before helping her find a way out of it.