ltr called me earlier. a minute or two into the conversation she tells me she sees an ex classmate on campus. I hear them start small talk (hi how are you good what class do you have next) followed by her hanging up on me. 5 minutes later she calls me, I don't pick up and she texts me saying sorry for hanging up

since then I've been ignoring all her calls and texts and now she's asking what's wrong. am I over reacting for feeling disrespected? I'm not worried about her cheating or shit like that, it's more the fact that she hangs up on me out of nowhere to randomly talk to an old classmate.

I don't think she realizes what she did but she knows something's wrong but I don't want to tell her it bothered me obviously. what's the right approach here?