Family visit

So today my Mum in law and sister in law came to visit on way to hols.
My sister in law has a little girl.
Then my daughter and Grandson came to visit...
Then I was trying to work out the relationship of these two.
At first I assumed they were cousins... No. Tyler's mum is Millie's cousin.
So is Millie Tyler's Auntie? Or one of those third cousins four times removed type of things?
Confused.com :)