My girlfriend thinks I like another

As you can see from my title, my girlfriend, that I love with all my heart more than anything, thinks that I like another girl. This is other girls name is "Brittney Poe." I don't like her, actually I hate her. I tell Erin (my girlfriend) that I don't like Brittney, and that she (Erin) is the only one that I want. No one else in this world makes me feel like her.
I wish some way, some how, that I can try to convince Erin that I truely love her, and not Brittney.
Sorry for any misspelled words, like that one, but I'm not very good at spelling.
Hope all is well for you,
Boone

Seem's a bit childish to me, if she doesn't believe your promise - then you have to ask yourself why, and more importantly, get to grips with her as to why.

agree with sarah unless you gave her a reason to be suspicous she just being stupid childish or paranoid if you told her already and she still doesn't believe you just try to play it out smoothly if Erin hasn't dumped you yet but she thinks you like brittney then she most likely won't just keep denying that you like brittney

Shes obviously either

1. paranoid
2. an attention seeker
or
3. got really low self esteem

Are you sure your prepared to fight a constant uphill battle with someone over no reason??

i don't want to sound immature by all means, but when i was going out with my then-boyfriend i thought he liked another chick. we argued about it all of the time, but he mostly brought it up in the first place. and i only thought he liked her because i was still shocked that i had such an amazing boyfriend and i didn't want to lose him. if he would've just told me that he really didn't like her, i would've been cool with it.
but try not to flirt with brittney or mess around with her. and when britt's around, really pay attention to erin. don't even acknowledge(sp?) britt's existense. and just tell erin that you love her with all of your heart and you would never do anything to hurt her (ONLY if you really mean it)
hope i helped XD
lauren

If you have told her you only love her and she doesn't believe you, that's just plain stupid. All you can really do is keep telling her you only want to be with her. Look into her eyes with sincerity when you tell her how you feel and if she still doesn't believe you after that, then i don't know what else you can do. I agree that she is being childish. You just need to get it through her head.

I agree with Lauren here because i used to have this problem with my boyfriend. And I wasn't attention seeking or immature, I had come out of a really bad relationship and stuff had happened to me over the holidays so i guess it was my self esteem thing. The only difference with this was i thought this girl liked my boyfriend and shes one of those pretty intelligent girls which all the boys would die for..and i knew her and my boyfriend were close anyways. To cut a story short, he gave me reassurance (although sometimes he got irritated with me) and now i'm fully secure in our relationship..and as it turns out this girl did like my boyfriend!! Not saying you like this girl, but i suggest you give Erin reassurance when she needs it even if it annoys you. Maybe talk to her about her feelings too..

Either she want's more attention from you, or she's really insecure.

If she means all the world to you, just show her a little bit more of love, but if she pushes you away, what use is a relationship?