Captain Miss Fortune Skin

They always do this with skins.Riot release them throughout the patch cycle rather release them all the day the patch goes live. The Capt. MF skin will likely become available for purchase once Act 3 of Burning Tides happens,which isn't for another few days.

I was hoping that this new skin would replace her old default skin...

You didn't miss your chance. Skins usually aren't avaliable just after the patch. The skin will most likely become avaliable once act 3 of the bilgewater event hits the servers(in 2 days)

I thought that the boots looked a little weird on this skin.. I was thinking like boots that go up to the thigh.. so she looks less Aristocrat and more like a Captain of Bounty Hunters. It can be tight to her legs and still be sexy, but I feel that it would look more natural on her.