Is it normal i miss a girl i barely knew ?

Around 8 months after coming out of a long term relationship I met a girl out of the blue, she was funny, witty, and very sweet. We met up and got on from the start, she was innocent and not like any girl I had met before. We went on a few dates and things were good at the start, but it got to a point where I wasn’t sure what I was wanting.. she was a good girl and I didn’t want to lead her on to break her. She didn’t throw herself at me and I was wanting a girl to do that. I wanted something casual, something fun, something exciting. Alex was just a timid girl and although she’d done nothing wrong for me the spark was fading.. I hadn’t finished things with Alex but another girl popped into my life I wasn’t thinking about getting with her at the time but she seemed exciting so I cooled it with Alex and told her I didn’t want anything from her, I said a load of shit if I’m honest because I knew she was falling for me.
She begged me to stay and it was hard for me because although she was a really nice girl I just wanted something with more power.
Me and the new girl Kelly we got on so well she had fire in her belly. We met up and she was the complete opposite to Alex.. things were good and yeah she did throw herself at me and it was amazing. I’ve been with Kelly for a good 5months now, nothing official but it’s just the same old shit. I feed her she gives me sex, she’s not even bothered about going out on cute dates. I keep thinking back to Alex, how I loved her banter, her timid ness, the way she held herself, the way she looked at me, the way she never let me in, the way she didn’t throw herself at me, the sweetness, our cute dates and giggles. I miss her. I thought I’d completely gone off Alex but I think it took Kelly for me to realise Alex is a pure woman.. something I took for granted, a girl I really hurt, I keep wondering how she’s doing what she’s doing, Even though I thought I didn’t like her? Is this normal?