Have you thought of inviting her for coffee or tea? That's a next but non-dangerous step. Take it from being an impromptu chat to an on-purpose chat and see what happens. At the worst, you find out you're not attracted beyond neighborliness. I have a neighbor who has become an excellent friend. He's a year older than I, has a much younger girlfriend, and is very religious. While he's nice looking, we are clearly not type for one another. Even so, we have swapped phone numbers. He comes to my aid when I need something heavy moved and I lend him my ladder when he locks himself out of his apartment. That relationship works great for us.

We have a very crappy emergency siren here. She had expressed a concern about not being able to hear it if things got ugly for whatever reason. I told her that I'd help keep an eye out for her.
Wednesday night we had a bad storm roll in at midnight. It was the fun kind with a tornado being drug behind it.
I went outside and rang her doorbell. She came down, gave me a thumbs up and went back upstairs to hide in her bathtub.
That was my brave, stupid, but sweet reaction to the situation.

Sometimes ..that’s as good as it gets…

Is she hot?

Sometimes people do not like to complicate their situations by getting too involved with a person who lives in their building or someone that they work with. That might be the case here. Just food for thought.

Test the waters a little by asking if she wants to catch up by going out for a coffee on the weekend, or come downstairs for dinner, because "it's easier to cook for two". If she says no, then nothing lost but if she says yes, see how that goes.
The biggest indicator though is touch. Does she touch your arm when talking or your shoulder when saying goodbye? If she doesn't do it to you, try doing that to her. Just a gentle touch on the arm when saying goodnight/bye.

Tough call. You never can tell if someone’s just friendly. Though I do agree that that’s a LOT of talking. Do you find her attractive? Maybe find some way to slip that into something you’re talking about and see how she responds?