You've been talking for months. She's responsive, occasionally warm, remembers things you've said. But nothing ever advances. Every time it feels like it might go somewhere, the moment passes and you're back to the same low-level contact.
You're not being rejected. You're not being pursued. You're just there.
The game
She has a primary pursuit (someone she's more interested in) and she's keeping you available in case it doesn't work out. The bench isn't a holding pen for people she's indifferent to. It's for people worth having around if things open up.
Maintaining you costs almost nothing. A reply here, a reaction there, enough warmth to keep you from writing her off. You stay available. If the primary pursuit falls through, you're already warm. If it doesn't, the bench just never gets called up.
Your position is harder because genuine interest and bench-warming look identical from inside them. Both involve real warmth. Both involve occasional forward momentum that goes nowhere. The difference is what's happening offscreen.
The equilibrium
What keeps this stable is that the contact is calibrated. Not enough to push things forward, exactly enough to keep you from moving on. If she went colder you'd stop waiting. If she pushed things forward she'd have to actually choose. The current temperature serves her position without requiring a decision.
Dominated strategies
Trying harder to advance things. More investment, more effort to create a moment. The reason nothing is advancing isn't uncertainty on her end — it's that she's not ready to choose. Pushing doesn't change that, it just increases your cost.
The only move is to not be on the bench. You can't advance from it, you can't see the timeline, and waiting costs you time pursuing other people. Treat the lack of progression as the answer and act accordingly.