Praying for the wrong person?

I went to get my mail this morning and there was a notice of the death of a neighbor, whose name I am very familiar with, and who I THINK I knew. It must have been sudden; I would have heard she was sick, that's a popular subject in the laundry room.

If she's who I think she is, she was extraordinarily kind and patient with my mother once when I took my mother to her place of employment and my mom was confused and anxious and needed kindness and patience from the whole world just then. I've commended her to God for that silently, in my heart, when I've passed her in the driveway or hall (and thanked her out loud, too) and I now pray for the blessed repose of her good soul.

But I might have the wrong person. I can retain names, facts and faces but not assemble them in the right order. The woman I'm thinking of I might see again! It will take awhile before I'm sure; the dead woman is so well-known in the building that I will be a little embarrassed to find a neighbor in the common areas that I can ask "So, was X the lady who worked at Y? And had blonde hair?" I SHOULD know, darn it.

So if I pray for the soul of my neighbor, but she's not dead yet, does that mean wasted prayer? Obviously, no prayer is ever wasted, no conversation with God is a loss. If she's alive, then the woman who did die (who I probably knew, too) needs prayer as she meets the Mercy and Justice of God. Loving a family member, even the wrong member, in the Body of Christ in prayer can't be wrong, because His Spirit flows from and through all of us back to Him, Its Source and Destination.

It is therefore a holy and wholesome thought to pray for the dead, that they may be loosed from sins.
- 2 Macc 12:46

UPDATE: It was her. Eternal rest grant unto her, O Lord, and let Your perpetual light shine upon her, may she rest in peace, Amen.