OP i'm sorry you've received a few post responses here dismissing the possibility of bisexual feelings. Some of these replies sound like straight women who refuse to acknowledge that women can have genuine romantic and sexual feelings of attraction towards another woman, and why downplaying lesbianism/bisexuality is so dangerous and society doesn't recognise wlw relationships as much as heteronormative ideals.
To suggest you are drawn to the lady because you view her as a mother figure is insulting since you clearly view her in a romantic light, and your feelings are valid.
Your being in a relationship with a man currently, and her being partnered is obviously problematic (but you have already stressed that he is aware of your feelings). No judgement here in that case, who are we to criticise the workings of your relationship.
I think the most important thing is to be honest with yourself and trust your own instincts in your clear attraction to another woman. Yes it may just be the one, but it doesn't make it any less valid. Clearly it is more than platonic admiration since you have thought about being intimate and even having sex with her!
I don't have much to advise in terms of pursuing things, work crushes are always risky and it's not advisable to cross these boundaries where you work....
I don't think anybody should be trying to define your sexuality on here, since it's a very personal and individual thing.
It may well be that you are bi-curious, and you may wish to explore this further (with a single lady/ideally if you're single/with partner's acceptance) with a single lady. Life is too short to be unhappy and wonder 'what if'!