My girlfriend offered sex as a birthday present and it disappoints me.
What about her offer upsets you?
She's a slut for even offering sex
First of all, you should not call her that. Secondly, it is rude to judge someone for offering you something that you already have done. Sex is not a horrible gift, especially if it is with your girlfriend.
Well she also wants to come over and feed me with food. It doesn't sound that bad.
You might not appreciate her offering sex, but that doesn't give you justification to demean her and call her names. It sounds like she cares about you and making you food is a great gift, too.