Is this crush transference? Or genuine?

Sorry for length of this but would really value input.

Im 25 and work for a non profit it in Scotland. We have interns work for us for about up to 6 months and they often are young college girls. I told myself when I started thus job only 7 months ago not to get involved. I haven't much dating experience, I was raised a jehovahs witness where dating is with the intention of marriage and left in my early 20s. I have lost all my friends since leaving and found it hard to make friends and get to know people since.

Anyway, in Aug a new intern started, I'll call her S and she was breathtaking. I became completely captivated by her. It was the biggest crush I've ever had, she was all I thought about.

I didn't really hide that I wanted to spend time with her but didn't make a serious move.

A few weeks later another intern started. She was my age and from Mexico. I'll call her M. I thought she was pretty and quite cool but was so obsessed with S I didn't think too much of her.

Over time, I got to know M quite well I found her so funny and talked a lot and became good work friends.

With S, she was nice to me but nothing more.

The day after S left, with me still feeling madly in love, after months of holding it in and not telling a soul I asked M to meet for a coffee so I could tell her...I wanted to get it off my chest but also curious to see if she picked up on it.

M wasn't surprised and wondered why I never made a move. I explained that as we worked together, if she said no it would be a very awkward work environment and also, I'm not someone that just wants to sleep around and she was only a temp intern and there would've been no future after she left.

M then asked me why specifically I liked S. I'd always told myself it wasn't just physical, that it was deeper than that, that I was better than that. That I liker her personality and soul. But I couldn't really think why. I described a few things and ended up describing M. I realised at that moment it was just a mindless crush, a physical thing probably and nothing more.

S has been away for 8 weeks or so and the crush fizzled out very quickly. She's just a normal girl to me now in my mind. Not as special that I had thought. Not The One.

Over this time, I've gotten to know and respect M a lot more and found myself caring about her.

A few days ago M and I went on a day trip to the countryside. We both had an amazing day and as it went on I started feeling more and more for her. There was a moment where we were sitting on top of a hill, alone and close together and she just became silent. Normally she's very chatty. I really wanted to kiss her. I didn't. She's going home in a week. It would've also been a horrible, awkward 3hr journey home if she rejected the kiss.

Also, in the back of my mind, I'm worried it's the same situation as I had with S. Although, as I said, I know M a lot more. M was there all along, right under my nose. I'm just very confused. I've no idea what's going on with me. Would love to know what you think? In the future at work, I might just need to be very distant with new interns as can't keep going like this.