Why is my coworker acting strange?

So I (M) and my friend from work (F) are both in our early 20s and have worked together a few years now and are very close friends. We're both in relationships and as far as I'm aware have zero interest in eachother in any romantic sense. We get eachother (and only eachother) gifts for birthdays and Christmas and text pretty much daily, however, despite being good friends, I've noticed that she acts odd with me.

For example, she's a very energetic, touchy, bubbly, grabby kinda girl, and is very handsy with people and doesn't mind when people are touchy back, but if I ever so much as accidentally knock into her, she recoils as if she's suddenly super uncomfortable that we made contact even though she's happy to touch me often and is OK with other guys we work with regardless of age, looks or her opinion on them touching her, it's just myself.

I also get quite a lot of attention from female clients and compliments and offers for drinks, requests for my number etc and while it's flattering, I've got a girlfriend who I adore, so I politely always decline but appreciate the ego stroke. However, when this happens she always puts it down and tells me not to look into it, or not to get an ego etc, or if I mention I think in good looking she'll scoff at it and every now and again I'll hear her make a joke about something, whether it's what I wear or something about me every noe and again to a work colleague just in earshot.

Basically I just find it strange that I know I'm an attractive enough male (not a model, but also enough to never struggle for female attention and compliments) and we're very good friends, but yet she always plays down my looks and is so almost disgusted if we touch in any circumstance. I've got a playful, cocky attitude, but it's also not extreme that it needs to be reigned it, just the odd fun comment every few weeks. But does anyone know why my friend has an issue when it comes to my looks or us touching?

Why is my coworker acting strange?
Post Opinion