You work at the same company, doesn't matter if it's the same office or not, I wouldn't do anything with it.
However, if you actually want something to happen then take some initiative and have some fvcking balls man.
You are being so timid and passive. That is a huge turn off to women. This women isn't fvcking stupid. She knows you like her. Either ask her out and get your answer or stop it with this nonsense.
I mean what's your plan? Wait for some magical time when the stars align and everything lines up perfectly for you?
That time is never coming. I mean what kind of man builds a plan of action on someone being promoted and then going for drinks, as if that's something that happens every day? Like that's literally your plan to get her to go out with you...you can't be serious.
Bro, grab your balls, be a man, face rejection and ask her out. If she says no then leave her alone.
It's that simple. You are delaying this because you have this fantasy in your mind that she MIGHT be interested and you can keep convincing yourself of this because you have taken no action so your mind can have these fantasies about what COULD happen that would not be able to take place once you got your answer.
But having fantasies about an outcome doesn't get you closer to that outcome, it only wastes your time. Stop wasting your time and be a man of action.