IIRC Aya leads with Muk and Tentacruel, so I would probably lead with Donphan and Unfezant. assuming your Unfezant can outspeed the Tentacruel. If it can try going for Air Slash on the Tentacruel and having Donphan use EQ. The best situation would be that Tentacruel flinches in which case you minimize the amount of damage you take in the opening turn, while potentially OHKO her leads. If all works out, you theoretically have an answer to most of her Pokemon, just watch out for the Sludge Waves and Spike/Toxic Spikes.
On the case that Unfezant does not outspeed her Tentacruel, might be best to simply lead with Klang and Ampharos (Replace Pyroar since its probably won't be useful in this battle). If you have any Ability Capsules that you can spare on hand, there is also the option to switch their abilities to Minus and Plus respectively just for this battle so they can get a 50% SpAtk boost.