It’s probably best to be straight up and ask. But if you don’t want to do that, you could just mention her up in passing. Such as “Hey did you see what Anna posted?” (let’s say Anna) or maybe some thing like “hey I literally thought I saw Anna at Walmart” and then when this person is somehow brought up, you could be like “speaking of which, I didn’t see her at the party? Everything okay?”
"Complex" is used here to describe the group of apartments. So, it qualifies for describing a noun, like the definition of adjective. Let me know if you got it right.
