There's a good chance that her attraction for you may have expired, so don't burst in guns blazing with a direct opener. She may have taken your "no" as a rejection, so you opening her direct probably won't align with how she sees you, so you'd appear very weird in that case.
Observe her the next time you see her. Does she try to make eye contact with you even though she may not be smiling? Does she seem observant, as if trying to figure you out? Then there may be a chance that she is still interested in you. I mean, you two have been flirty in the past, so it's not like you're popping out of nowhere. So if there's something about her walk, appearance, apparel, or whatever you find complimentable, give her a genuine compliment. Perhaps even a "you're looking stunning as always" might work as a good opener. If you feel like a compliment may be a bit too strong of an opener--maybe she appears very cold--then skip it for now. You can save the compliment for later after you get her to warm up a little bit. If you skipped the compliment, just say hi. Ask how her day has been so far and ask if she's doing anything exciting later on in the day or something like that. Make short small talk. Here, I feel like it would be best if you held back on your sexiness a bit due to that alignment issue between how you come across and how she sees you. Like, if you haven't flirted with her or interacted much with her since the "no", then she may believe that you have no interest in her, so turning your sexiness to overdrive may appear very strange. Nonetheless, show great eye contact, posture, and smile, but don't put on the "you have no idea how hard I'm gonna make you cum" eyes or the bedroom voice just yet. When the small talk dies out, go with that option 1. Then you can switch on your sexiness.
The above feels a little scripted, so in summary you want to:
- Gauge her warmness/openness/interest level
- Open accordingly
- Adjust accordingly the amount of sexy vibe you project
- A little bit of small talk may be necessary to warm her up a little
- Don't lollygag in expressing your interest--it probably has dragged on too long already
That's what I can give you with my current level of knowledge and experience. I hope things go well for you.