How old is Lilly?

Lilly, before she ran away for seven days, used to walk up to the sliding glass door, trying to get into the kitchen. One day she flipped over, and I took advantage of this moment before I turned her over.

I've had Lilly since 2016, saving her from a family that kept her in a salad bowl. She was grown, but grew even more since 2016. Can someone tell me how old she is?

Thank you in advance.