I get jealousy towards cis women, I really do. It's a burning constant in my life, the oldest form of gender dysphoria that I can recognize in my life. I get how it can feel to look at a cis women and feel like you could do it better where you born in their genes.
It's a fact of our existence as trans people that our expressions of our genders are constantly policed and belittled. Every little variation from what people expect based on our assigned sex is a target for scorn. It's wrong that this happens to us... but I think it's also wrong when we do it to other people, it hurts not only them, but us.
Take the woman you work with. You say that she isn't doing anything with her womanhood, but she is, being a tomboy is a perfectly valid expression of who some people are as women. It may not be what you would do or want, but it's just different, not "nothing." By excluding her from femininity for her expression, you're contributing to the same garden that other, more overt, forms of gender policing are gathered from.
I'm not saying it's wrong for you to have these feelings. You feel how you feel, and you don't have to change that to please anyone or align with any social justice goal. I just think that by reframing the issue, by seeing that she is a woman expressing her womanhood, you will expand your definition of what constitutes womanhood, and your dysphoria won't chafe as badly over this issue.