Overnight Couchette

I never used a Eurail pass, but while living in Europe 30 years ago, did the second class couchette with my family.

The compartment is for six, not four persons.
https://www.seat61.com/sleepers.htm

Also, you cannot lock your compartment, so protecting your valuables requires some innovative thinking. We used a small back pack as a pillow and i spelt on it with passports, cash, etc inside.

Couchettes work a lot better than trying to sleep in a regular first or second class seat.

You get sheets and a blanket and sleep on a padded mat that is comfortable enough. You sleep in you clothes instead of pajamas. I wore loose fitting exercise clothes. The toilet and shower are down the hall, not in the cabin.

It is far more economical than going first class, but you will have company in the compartment.

Gary, are you saying she already has a Eurail pass for that time period, or are you saying she is considering getting one?

Here is a link to the Nightjet service that runs from Munich to Florence: https://www.nightjet.com/en

And here is how to use eurail for the nightjet:
https://www.eurail.com/en/get-inspired/trains-europe/night-trains/obb-nightjet

You may also find this website useful for learning about European rail travel https://www.seat61.com/index-mobile.htm

More of the modern couchettes can be locked from inside, including these. And as Barbara's link describes, the second-class passholder can choose any type of couchette or sleeper, surprisingly even including the Deluxe category (which I would not choose to pay for). See also:

Women-only compartments: https://www.nightjet.com/en/komfortkategorien/spezialabteile/damenabteil.html

NightJet's own page about Eurail reservations : https://www.nightjet.com/en/buchung/tarifinformationen/interrail-eurail-paesse.html