Search Results: my ex keeps contacting me

So about 4 months ago, I was chatting to this girl I used to goto school with on Instagram. She used to date this one guy a few months earlier. Conversation was good and planned to meet up. All of a sudden she stops messaging. Then I noticed that I couldn’t see her stories and all her story highlights were hidden but we still followed eachother.

One night I hung out with a buddy of mine and he knows her too and he says to me “what’s up with _______. She’s hanging out with her ex again. She posted on her story”
And I’m like “huh? I didn’t see that on her story”. And then I put 2 and 2 together and realized she hid her stories from me. So clearly she got back with this guy and didn’t want me to see it. Maybe to keep me around so she could work things out with her ex and if it doesn’t work out she still has me as a backup?

A few months later all of a sudden I can see her stories again and she never posted anything about this guy. So I assume they ended it again. But she hasn’t made contact with me since the time she ghosted me.

The other day all of a sudden she replies to my story. We end up doing small talk but my responses were bland but she kept it going with enthusiasm, and yesterday she randomly says “I know we were supposed to hang out a few months ago and I’m sorry I was swamped with work and school and covid lockdown and I know that’s not an excuse but I’m sorry. When you’re free sometime I owe you a drink :)”

I haven’t replied. It’s so sketchy because I know what actually happened but she doesn’t know that I know she hid her stories and got back with her ex at that time.

What should I do? Keep it going and agree to hang? Call her out on it? Or just play it like I couldn’t care less if we met up or not and say “ya maybe sometime”. What are your thoughts on the whole situation?

I had a relationship 4 years that lasted for a few months. It was the only relationship I ever had. It culminated in us watching a movie together in my bed, cuddling and kissing during the night together. She broke up with me the next day, saying that she would rather focus on her career than a relationship. We were both premed. We were really into each other, but she started to ignore me even though I just tried to keep our friendship going. I haven't talked to her since mid 2017. I think about her sometimes and wonder if I should send her a text just asking how she is doing. Thoughts?