It seems pretty clear to me that she didn't drink the potion, but rather that the potion is very volatile and the fumes coming out from the bottle were enough to affect her. Drinking a mystery potion would be too silly for her to do. Plus, Elsa was quick to open the windows when she noticed the smell, and there was a ton of potion left in the bottle.
Anyway, while love potion shenanigans are a little cliche, I do like that our couple is getting a kick in the hay to make them get moving along lol