How do I add a new (additional) gmail calendar in to my iPhone?

I have a gmail calendar that syncs just fine.

My wife has a gmail calendar that shows up on my google.calendar.com just fine.

How do I show her calendar on my iPhone calendar, and have it update when she adds/deletes/edits stuff on her calendar?

She sent an invite on gmail, and when I open that on my phone, the calendar opens in safari and it shows just fine. The google calendar app shows it just fine as well, but I don't like the layout. I'd like it to show in the iPhone calendar as well.

Thank you in advance