Swashbuckler Opportune Parry and Riposte used to Parry Attacks of Opportunity against them

So my question is this.

If your Swashbuckler has the Opportune Parry and Riposte Deed, would you be able to use this ability to parry an melee Attack of Opportunity?

"Opportune Parry and Riposte (Ex): At 1st level, when an opponent makes a melee attack against the swashbuckler, she can spend 1 panache point and expend a use of an attack of opportunity to attempt to parry that attack. The swashbuckler makes an attack roll as if she were making an attack of opportunity. If her result is greater than the attacking creature's result, the creature's attack automatically misses....Upon performing a successful parry and if she has at least 1 panache point, the swashbuckler can as an immediate action make an attack against the creature whose attack she parried, provided that creature is within her reach."

Normally I would think that since an AoO is a single melee attack that you would be able to parry it. However if the AoO is triggered by something like drinking a potion, casting a spell or attempting a combat maneuver the way the rules are read I think the AoO doesn't stop the action, simply takes advantage of the opening.

So if you tried to drink a potion and someone made an attack of opportunity against you, would you be able to parry it, make an immediate attack against them (provided you have the point) AND drink the potion?

Yes, you can. But you finish drinking potion, making combat maneuver (etc..) after attack, opportune parry and riposte has been resolved. However I believe it would be reasonable if GM says you cannot parry and riposte if at the moment you are using your weapon for something else (like making trip or disarm with that weapon).

The wording says the proxy is when an enemy makes a melee attack against you.

Attacks come from taking actions, special abilities, and attacks of opportunity. Additionally, it's called an attack of opportunity. Just because it's an attack (made) of (an) opportunity, doesn't mean it's no longer an attack.

So it's valid for use with Attacks of Opportunity, regardless of what the Attack of Opportunity comes from (in terms of proxy). I will say that you couldn't use this if a creature is threatening with a Ranged Weapon via Snap Shot feat chain, since it's a Ranged Attack.

@ TheTheos: I disagree. The Parry and Riposte options do not make any specifications of weapon choice, it makes no sense . I could be an unarmed Swashbuckler and Parry/Riposte with my Unarmed Strikes if I really wanted to. After all, it's the world of fantasy. I could use my hands to stop a sword coming down at me, and then follow up with a kick to their calves to knock them on their feet. Giving Swashbucklers some interesting hand-to-hand combat options like the above isn't a bad idea. Of course, if they can't properly wield their weapon, say, a Two-Handed Sword, because one hand is holding a potion, then they can't make the Riposte with that weapon, but not because they're already using it, because they can't use it properly.

I do agree, however, that the resolution is Drink Potion -> AoO -> Parry -> Riposte, and that the Potion would not take effect until you finish resolving the Riposte.