annie is always a tough middle.. just because of her gay ass nukes, which can really hurt a squishy ashe..
there is a few alternatives to beating her. Either get 6 before she does, maybe help a teammate farm golems to gain a touch of extra xp. Or get xp runes like i do ^^
but i find good annies can take you down lvl 5, if they spam spells with mana regen. So the best thing i reckn is to spam back, ashe has a lower cd and higher range on her volley, use that to your adv. Try getting mana regen, keeping backing when annie approaches past creeps, and spam as much as you can from with your range.
OTher alternative... is to constantly spam her at lvl 1, 2 ish, with ur crits.. get her to waste her hp regen, and try and force her to make a lvl 4 retreat.. but that would be hard..
my second suggestion is your best bet mate.