<human>: Could you distill the essence of the text into 1-3 sentences?

Yesterday after another coworker mentioned that we always seem to be having fun while the boss is away so she must be the Monica of the group, 33F says very loudly that must make me (29F) the Joey of the group because I'm 'ok looking but really dumb'. She's quite nice to me when it's jut the 2 of us and even refers to me as her bestie but when others are around she often makes reference, out of nowhere, to my stupidity in front of others. She does it as if it's banter/ joking but it's never funny and I find it offensive. 

I'm quite self conscious about my intelligence and have fairly low self esteem lately so not sure if I'm upset about it because of that or if I am right in being offended and should actually say something, maybe next time it happens? What should I say to something like that? I'm also shy and slightly a pushover.
<bot>: Coworker says I'm Joey from Friends because I'm ok looking and am really dumb. Has often makes similar remarks. I am offended but am self conscious of my intelligence. Not sure what to say, if anything.