Loki is more intelligent, because as the goddess of trickery she formulates extremely intelligent plans with touches of trickery that allow her to come out on top of situations.
Although Hestia is extremely perceptive and intelligent (in the most critical and important moments), Loki in terms of intelligence seems to have an advantage of one or two steps above her.
As far as Hestia would find out about Dionysus, I sincerely believe so, because as I said, despite Hestia appearing to be an airhead, she is extremely perceptive and intelligent, especially on the issue of Dionysus (remembering that Loki only went to find out who Enyo was with the help of hestia, mainly because she knows how he really is)
