Which Naruto episode shows Anko in her curse mark form?

You mean in a CS2 mode?

No episodes as of yet; we're not even sure if she got the CS2 mode going for her Cursed Seal.

*Spoiler*

But I bet if she does have CS2 then she'll use it against Kabuto/Orochimaru later in the manga, as she is hunting for Kabuto right now, and this will probably be the last significant thing she will do in the series.

*Spoiler*

But if she had a choice she wouldn't use her Cursed Seal, maybe if she gets really angry or something and she can't stop it.