Then why didn't she stop when finding out he wasn't? For Luffy's sake. Also, there is a difference between being actively affiliated with Dragon and stating there is no way Dragon will stand still while his son is being executed - meaning assuming that Dragon will participate too - and Rayleigh, who retired for 20 years, with his captain being dead for equally as much time.
Not sure what the purpose of this thread is. We know Ray didn't come simply because he didn't care. Ace being the son of his former captain that is dead for 20 years simply isn't enough.
Also, why do you think Roger entrusted Ace to Garp, a marine, rather than Rayleigh? Even in their lifetime, Roger didn't see Ray as a babysitter for his son.