It depends on the women. A friend of mine says she can ejaculate when standing with her partner kneeling in front of her, fingers inside putting a lot of presure on her g spot while she masterbates.
An ex girlfriend could squeeze out a little cum on cue but not really ejaculate ( I was too young then).
I think some female ejaculation in porn is probably faked.
I would like to know how they fake it.