I've got a similar setup.
HEre's how I did it:
my wife bought all the Echoes under her Amazon account. They start off as hers.
I login as her to initially set them up (or user her phone)
in the Alexa app's settings, I connected her to her google calender
I made me an Amazon account, then I joined her household
I login to the Alexa app on my phone as me
I setup my google calendar under settings while I'm logged in as me.
Now, when either of us looks at the settings it shows the current user with checkboxes for which calendar sources AND additional family members and the checkboxes for their calendars.
Now, do the voice training for Alexa on your phone. Have her do hers on her phone.
This is how Alexa knows it is you asking what is on YOUR calendar, she recognizes your voice and switches to using everything setup under your account.
You can manually swap who's account Alexa uses with a voice command, but I'd have to look it up.