Am I overreacting that my gf told our co worker that we're not dating and she only dates black men (I'm white)?

The woman (F30) I (M26) have been in an unofficial relationship with for over two years, has refused to acknowledge our relationship on any official level, and doesn't seem to like being seen with me in public, even making comments about how she thinks people are wondering why we're together. We do all the boyfriend/girlfriend stuff but she won't grant me the label offically. We work at the same place and she doesn't want anyone there to know we're together at all.

A co-worker asked her if I was her boyfriend and she said no, and that she only dates black men (I'm white) I feel very disrespected and don't know how to react. I already know everyone is gonna yell "Leave her!" but she's amazing and I love her I'd rather work through this but have no idea how to approach something like this. Am I overreacting or how should I react?