If she truly is not getting any milk, then the value is emotional and psychological. But, you may not realise and she may still be getting a little bit. Have you asked her about that? About whether the milk has changed, too? It may be a way to feel close to you and comforted, but it may also be a bit of transitioning before she lets go.
Either way, it all depends on your comfort level with letting her continue. If you are fine with it, I say, why not let her decide when to wean? it will happen naturally over time, anyway. I would just let it be and let her guide me.