FWB for six months, but I just found out she has been in a relationship for eight months. 26F and 31M/26F

I've been seeing this girl for six months. We were friends, but then when her old job closed down she needed help getting through some tough days. One of the days, we had sex. And it continued, and we started hanging out more. <br><br>We never labeled it, but I've come to realize we are FWB. I've started developing some feelings for her. <br><br>I've always assumed she was single, as she doesn't wear a ring and is always alone. Until we were at the store and another customer asked if we had kids together (we were picking up food for her dog). She corrected them and said no, we are friends, and then she said "I have a boyfriend." I felt like I got punched in the chest. I wonder if they are as FWB as we are. It hurt so bad I said little the rest of the day. <br><br>A few days later, she posted a picture of herself with a girl holding a cake. It was her birthday party. I realized since she didn't tell me about her birthday, or her boyfriend, or her birthday party, I'm not important. I unfollowed her on social media. I've been avoiding her since, but she's been reaching out more. <br><br>What are my next steps in regards to her? Do I put myself out there and date? Am I in a position to say something to her? Do I end it?