should I be mad ?

Okay so I'm friends with my boyfriends ex and he knows it too . Today she randomly mentioned her meeting his mom at his grandmas and how they were talking (basically a memory to her) , honestly I was like okay but then again I was lowkey sad . I told him about it and he said yeah they did meet each other at his grandmas but I was lol okay and he said he knew I was mad because I didn't tell him but tbh I kinda am because he mentioned I was the first one they met . SHOULD I BE MAD ????