My Brother's Fiancee is A Pr0'stitute I Slept with, Should I Tell?

In 2012, I was transferred to Ibadan. I have lots of girlfriends in Lagos and don’t want to date any new girl in Ibadan, so me and my friend that was transferred together became regulars at a brothel.
Me and my friend had just 2 customers we patronize. 6 months later (early 2013) I was transferred back to Lagos. After I left, I do invite one of the girls to Lagos because she is too good in bed till I lost her contact when my phone got lost (December 2013).

We all traveled home recently for the Sallah celebration. I was surprised when I saw my younger brother come with the prostitute in Ibadan and introduced her to me as his fiancee...

I just stood there not knowing what to do because I was expecting the girl to feel somehow but she didn’t even show any fear. Throughout the day she was everywhere cooking and joking with everybody around there.

I thought she was pretending not to know me but I didn’t confront her, so I asked for some of her pix from my brother and sent it to that my friend if he knows the girl and he was quick to tell me that’s the girl I do "rough handle" on bed in Ibadan.
But when I told him of the relationship between my brother and the girl, he told me to tell our parents and my brother so they can cancel the relationship that the girl isn’t worth it.

Now am confused, I don’t know if the girl is pretending or she doesn’t recognize me anymore because of her numerous customers. I don’t know if I should tell my brother or just keep quiet.