You know, botch the check-my-LoL-account proposal. Either your girlfriend is so nerd she had a 9gag moment of correcting you and not noticing the names, or whatever, I don't know and I don't care. Instead, go to a jewelry shop, buy a ring that suits your taste (preferably personalised), then go to her in person, tell her some LoL lore and add some cheesy stuff like "This is the long-lost Zhonya's Ring, and I give it to you with my life." or whatnot. Make it up along the way but never give it her without you in front of her.
Nothing is more intimate than giving a gift in person.