Hi ejras
welcome to the Apple (user-to-user) Community.
Thank you for sharing the info on your Mac model ... wondering which MacOS version is installed on the computers.
Re: "Calendar sharing : how do we share each others calendar events?"
Apple support has articles online that may help:
NB: The articles below are for Mac OS 13 Ventura, else choose your MacOS version at the top of each article:
Re: sharing her personal calendar with you :
she may wish to share an individual calendar ... or ... the calendar account
How to: Share individual CalDAV calendars on Mac - Apple Support
or
How to: Share calendar accounts on Mac - Apple Support
More info: needed.
Ways to share calendars on Mac - Apple Support
In Calendar on your Mac, you can share calendar accounts with people who use the same calendar service....
Share calendar accounts on Mac - Apple Support
Keep your calendars up to date and share them with iCloud - Apple Support
All the best :-)