It depends on where you want to take this office fling.
If she is relationship material, you could meet discretely for a while and see where this leads. Texting or calling her is fine, after all you slept together so there must be some serious attraction at least. So go ahead and call or text her with plans in mind as soon as possible. Strike the iron while it's hot. There's little risk of appearing needy, unless you text her like 50 times a day
I would also advise that you should not engage in any risky behaviour at work, could get you in serious trouble... If she's not what you are looking for long term, you could keep it casual, and call her just for sex. Some of my fuck buddies have been girls from work, and there was no awkwardness, all the more it was kind of exciting to talk to them about work related topics when in a group at work and know that the night before we went to town on each other.
If you have no interest in her as a GF or FWB, just play it cool and let it die by the hand of time. It usually does, and especially if the girl is level headed there will be no consequences...
Whatever you choose to do, good luck!
