I suffer from Waswasa. If I accidentally made something impure and it transfers to my mom's wet hands while she is performing her prayer after Wudu, does it invalidate her prayer?
Bismihi ta'ala
One of the best ways of removing waswasah is never to accommodate to thinking of such scenarios. Do not create scenarios in your mind, and do not assume najasah at all. Your taklif and duty is to completely dismiss your shakk by ignoring it and considering whatever scenario you are in to be tahir and pure.
And Allah knows best.