The whole love potion thing is BS, and it's just a way for people who ship Harry with Hermione as a way to discredit Hinny because they're butt hurt that Ginny ended up with him instead of Hermione, and I'll easily debunk the theory right now.
Love potion is instantaneous. You drink it, you fall in love right away. Harry slowly developed feelings for Ginny over time. He just became aware of his feelings when he saw her kissing Dean. Had he taken a love potion, he would have been smitten immediately.
Plus, love potions smell like things that attract the person, and Harry smelled "something flowery he thought he smelled at the burrow" and later, when Ginny walked passed him "he smelled that flowery scent again". So it IS her he's attracted to, even without a love potion.
And let's not forget how he, Ron, and Hermione were on the road for months. He certainly wasn't taking a love potion then (or during his summer before he left to find the Horcruxes), but his feelings for Ginny remained. Had the been a result of a love potion, they would have disappeared once the affects wore off.
Plus, using a love potion is not only completely out of character for Ginny, but also something she would be very against since she knows what it's like to have your free will taken from you after her experience with Riddle's diary.
