As the title suggests I'm unsure on how to go about reporting a very obvious shill bidder/seller?

I've seen lots over the years but this one is so obvious it's not funny. The items are pre-loved kids/baby clothing so it's not simply a case of  having muliples of the same item. All the items that finish at under $10-$15 have a max bid placed by one of two 'buyers'....one with 0 fb and one with 1 fb. Both "buyers" have 100% bid activity with this seller. In the 31 completed items one piece has apparently sold then been relisted six times, another one five times.

She has well over 1000 fb and I don't understand why she doesn't just list them at the minimum she'd like rather than starting at $1 and shilling?