The last skin she got was Eternum Cassiopeia and her other skins are all pretty bad, Jade and Mythic cassiopeia have very VERY subtle effect changes but only one of her skins is 1350 and not to mention the other 4 are pretty outdated.
I feel like she might be hard to make a skin for or something, it's kind of hard to make a skin for a Lamia but it's not like she's horrifically unpopular, in desperate need of an update or something. She's at least middle ground popularity so i'm kind of curious why she hasn't gotten a skin in almost 2 year's. She's certainly not the only one but i recently picked her up and enjoyed her but i don't like her base skin much and none of her other skins are super appealing so i thought id ask about it.
Side Note: There's a lot of champions that seem to be left out of Skin Events simply because they're hard to make skin's for. Primarily because their base design has so many core part's that there isn't much you can change, swain NEEDS to have wings when he transforms, for example. And illaoi will always have Tentacles as another example.