GF (28F) laughed about my (27M) penis size with male friend. Do i stay with her?

Important info:
My gf and i have known eachother for about 2 years and been together 7 months.
Before we were together we have had sex a few times. We are from different countries and she came to visit me in my country a few months ago.
Recently my girlfriend wanted me to delete a girl im friends with on facebook that i had sex with 1 year ago before we were together. I didnt talk to her for a year. Anyway i removed her as friend.
Long story short:
I believe in projection so i ended up going through her messages on instagram.
Turns out she had replied to her ex texting her a few times (which is fine by me, im not a jealous type)
But i also looked at messages between her and a male friend that was sent just a few days before she was coming to visit me.
She was explaining that she was gonna get birth control for my sake because i dont like condoms. (I didnt ask her to do this, i had no idea)
The conversation was something like this:
GF: I think because he is thin hahahahaha
GF: I dont feel anything hahahaha
Male friend: Hes small? hahaha
GF: Hmmm thinnest i´ve been with hahahaha…
Keep in mind this conversation is from before we were together. But a few days before she came to my country.
My pen*** size is very average and im not insecure about it at all but obviously seeing this makes me feel horrible.
When i confronted her she had some explanation that her ex was really big and first times we had sex her vag*** was more loose but now it has become smaller and she feels it when we have sex.
For the record i think our sex life is fine and i believe she feels it and i do love her a lot and we are perfect for eachother in many ways.
But seeing this just makes it super hot to move on for me and i dont know if i should just cut my losses and end it here or try to get over it.
I dont really want to talk to friends about it because its embarassing and its gonna look like i have a tiny di** lmao.
I need some advice what to do here. I´ve told her i have to think about it whether i can stay with her or not.
Throwaway account for obvious reasons