When we pray for someone to be healed, we pray this individually in the Amidah but we also often have a community mi shebeirach list. I assume that there is a theological reason for the public prayer, and not just to publicize who might need some extra support. This is true especially because you likely have no idea who Plonit bat Sarah is without further context.
Similarly, we often have more than one person praying (individually) for the same person, and they know about each other. Do the extra pray-ers help?
What is the benefit to having more than one person pray for the same recipient, either through the public mi shebeirach or through multiple people's private prayers? Surely God, who is just and merciful, would respond to a single prayer for a good cause. Surely, being all-powerful, He does not need to manage a queue where popular requests are dealt with first and multiplied prayer 'votes people to the top'.
Does God care how many of us pray for a particular person? What is the effect of the multiplied prayer?
(Question prompted by this answer to a post about asking others to pray for someone.)