Only if the eggs are still inside of her. Seriously...that's the only way to make sure the semen covers them all, and even then, it will still take a few days. A man can only produce so much at one time after all.
oh god that's disturbing. It also makes you remember that shes technically a frog.
Actually, she isn't. Suwako is neither biologically a frog nor related to frogs, and her abilities and divine influence/patronage are also unrelated to frogs. She just happens to like them and use them as a motif.