Hi @Grizwold225. Does your wife have a Google account linked on her phone? This can be added by going into Settings > Accounts and Backup > Manage account > Add account. Once done, open the Calendar app and then tap on the 3 lines in the top left corner and then add the Google account from there. Hope this helps!
@Grizwold225: If you open the Calendar app > Tap the 3 lines in the top left > Tap the cog symbol in the top right of the pop up window > Add Account > Google, then go back and tap the drop down arrow next to the Google account, can you select the Google Calendar now?