Stats are recalculated at the end of the battle. I can't confirm that you gain evs at 100 as I have nothing that high in this game that does not have evs but I can confirm that the stats change at the end of the battle rather than on level up.
@/Zer0 Yeah, she just basically tells you.
Yeah, I was thinking that the only way to see any improvement in a Pokemon's stats while EV training would be when it leveled up. Of course, that would be impossible for a lv100 Pokemon. I guess my post was rather redundant because I answered my own question; the girl who tells you the EV progress of your Poke is all you really need in Generation V.