Older woman doesn’t know how to communicate or maybe she does?

Met this older woman around the end of last year and we hit it off and told her that I was attracted to her and she said it was mutual. We agreed it would only be sexual considering our age difference and where we are at in our lives. With this kind of relationship open communication would be easy right? At least I thought I was being open. I found out pretty early that she had a guy that she had already been dealing with but I didn’t know to what extent. She told me she was heartbroken by what he had done to her but didn’t really think much of it. Then out of nowhere her messages got shorter and she stopped interacting with my post which she would like my post all the time and it was just noticeable the decline she took. I would ask hey is everything ok? She would say yea it’s not you it’s me and my mental and it’s just been a lot lately… I believed it for a second but I knew she wasn’t fully telling the truth. Few weeks go by and I can see she’s making an effort again but still there is something missing. She’s leaving information out. We play this game of cat and mouse of when we will see each other and it’s always an excuse of how busy things are. Finally I find out she has a bf!!! It all makes sense to why she was being so weird with me. The thing is why? She didn’t have to do that. Now I feel that she lied to me which she did and if roles were reversed all hell would break loose. I think she’s trying to keep me as a back up in case things go really south with her bf like a safety net. Just wanted to rant about that really quick. Found out she had a bf tonight and it’s been on my mind and I texted her asked about it and she hasn’t replied so we will see what transpires in the next few days. I guess age isn’t a great indicator of a person being willingly transparent.