Hi and welcome to HCM.
This is simple. When diagnosed with mono people should rest for at least 6-8 months and she should do it too. There is a reason why this is recommended. Every infection which damage liver
is treated by resting because then liver doesnt need to produce all these proteins
and can heal spontanuesly.
Mono attacks liver too and she should check liver tests every month till normal range of it. There is no other way to avoid complication of mono infection.
Hope I have answered your query. If you have any further questions I will be happy to help