you should be lucky that you have sucha smart gf.

the grammar and spelling you use when telling a lady you love her is VERY important. we see it as "I luv u" or any misspelling of "love" means you don't mean it. sometimes not spelling you out can seem a little careless as well. next time you should try something like "hai hai I got something important to tell you" and shell be like oh oh and that's when you say "I looveee youuuu" all cutesy like. chicks dig it ;)

She's a grammar nazi?

LOVE LOVE LOVE your name OP. And don't be offended. I sure she didn't intend for it to bother you. I correct people out of habit, with certain things.....but only verbally. My written grammar is somehow much worse than my spoken. I screw up good/well all the time while typing, but not while speaking. My point is, she probably hadn't even realized what you said until after she corrected you. :)

THAT I love her

It does. Lol! I never noticed that!

We correct only those we care for.

Hey... I know it has been said already but how can you get "I love you" wrong??? Even in french guy: "Je t'aime" tu ne peux pas rater quelque chose comme ça c'est très primaire. The only thing I see, is that you started to say something more than just "I love you" and she corrected that... oh well, it sucks and she's a pain for correcting you lol. I'd do the same though...

Learning is from life experience. Now you will not commit the same mistake next time. big baby

I must wonder exactly how dreadful your grammar must be for you to get "I love you" wrong...