Do you think evolving an eevee now will have a better chance to turn into a Flareon?

No

Highly unlikely, but I don't know for sure...

Although I think it should not be the case, but for me, more than half eevee evo turned into Flareon...

I think I actually have fewer Flareons than the other two, but I can't log in to get the actual numbers.

Oh, you mean during this fire/ice event. Hmm, I doubt it.

I've evolved one, Flareon. During the water event got Vaporeon, but I don't remember if it was just one or more.