The answer's very likely that no, that doesn't count.
It isn't the kind of help talked about in the Asking for help section, where you actually join the combat and are at genuine risk of suffering Bad Things if you lose. Vitally people can refuse help offered this way, and limit the elf's ability to gain bonus levels.
Interfering with combat by playing cards to benefit the player involved is, however, called "help". But there's lots of other risk-free things you can do to "help", including telling the player to use their own consumables, or getting them a glass of water to help them think and focus on combat.
Ultimately if this comes up it probably should be resolved by a loud argument with the owner of the game having the final word. I would probably argue against it, since elves will have an unstoppable, risk-free ability to gain quite a lot of levels.
(To your title of whether you can help and win the game: you can't reach level 10 by helping this way as an elf, as you didn't kill a monster yourself, you just helped someone else who killed one.)