"we" can play? umm.
Do not go there. She does not want to touch their bits for her animal's health. Keep the smegma to yourself.
No idea about horses but two years look a long time. They could have some big bean to be taken out, irritation, etc.
There are users here who are in animal rescue and could give some good advice if they wished, but they are also quite happy to set in dumpster fire flames users with messages like this ?
What I would do is, next vet run, explain the situation, that you want him/her to do the cleaning, check everything and show you howto so you can mantain them from now on.