Coworker wants to [F]uck [M]e after work. How can I say no?

This girl is amazing. The best kind of coworker, the kind that grazes your dick with their hand as the walk by. The kind that responds with “you” when you ask them “what do you wanna do.” The kind that takes every opportunity to get you hard tease you or turn you on. She is super sexy and more than that she wants me bad.

We have been working together for a while now and we have been close ever since but the other night we had been texting back and forth. Flirting and talking dirty leads to her sending me pictures of her bare naked body, her using her vibrator. She asked me to step away from work so she can see my dick. I obliged. I think I stayed hard all day long. Work was coming to a close and I told her to come by the office after work. She wanted it as bad as me and she simply asked me what time.

[M]y friend wants to [F]uck me and told me to post it here

This all started fairly innocent. My friend is a bit younger than me and she in a relationship so our conversations started off casual at first, we are in a situation that causes us to spend a lot of time together, so once we both realized how much sexual tension there is between us they progressed from there.

Simple dirty talk at first, "After you fucked me, before you cum I would pull you out and finish you with my mouth." and other things similar in nature. It progressed from there, exchanging pictures back and forth, her asking to see my cock and me wanting to see every part of her body. Sexually we are both into the same types of things, trying new things, exploring each other has been super exciting. She is the type that feels super confident in sexy lingerie and has not been afraid to show me her body whenever I ask. That turns me on more than anything: A girl who knows exactly what she wants and isn't afraid to tell you (She isn't afraid to tell you how sexy you are and what she is thinking about). I honestly can't help myself. There is so much anticipation even for the smallest touch or look, it is wild.