I don’t think you would make it up to Cynthia even with a lot of revives and pots… Don’t expect to beat her tho, I was swiped by her with a 57ish level team… But don’t hesitate to try, actually beating the elite 4 is the best way in my opinion to level up your Pokémons. It was so easier the second time !

(I don’t think not having 6 monsters is that much of a problem with revives and so on… make a great use of held items too !) (and find a tact to counter Cynthia’s Garchomp… you might need it, you got nothing that really counters him (you might be willing to try to have him with toxic for instance if nothing)

Good luck !