I think you've moved the goalposts too far!
The guidance with gel is all in the leaflet in the carton. It says what she's told you.
It says - 1) wash your hands and 2) no skin to skin contact with anyone with the areas of skin where it's been applied, for one hour.
@HelpMeUnpickThis Once it's on your skin, you shouldn't have skin to skin contact for an hour with anyone else, or shower, or swim etc as it takes an hour to be absorbed.
This is relevant for if you're cuddling your children or your partner and have just applied it to your shoulders or inner thighs and your skin is not covered with clothes.
If you want to use the plastic cap, that's your choice but it's not necessary.
By the time I've applied it to my skin my hands are almost free of it anyway.
I'd be a bit concerned about using the cap simply because the gel has to be spread thinly.
There used to be a guide in the leaflet years ago showing the area it should be spread over (but it's not there now).
Don't you find it takes ages to apply with something as small as the cap?
But it's your choice, obviously.