I really need some advice

How old is she? Is the whole film overtly occult or is it just a random scene? I wouldn't worry if it's just a one off scene, but if the whole thing revolves around the occult then maybe.

As far as you know is she a Christian? If not the best you can do for her is to pray for her. If so then try explaining to her how God wouldn't like it if she was watching things like these.

Pray without ceasing.

Would your parents help?

Are your parents Christian? And how old is your little sis? If she is under 13 or 14, I wouldn't even worry about it. Tarot cards mean nothing to a little kid, they are just a bunch of cards to them...but really, when she gets older, have your parents talk to her about it...or someone whom she looks up to. Really pray over this...be a good role model for her, that's the best thing you can do.

It depends, if she is able to understand the difference between such fantasies and reality, it will be most unlikely that she will treat it as a role model. In the same way that a violent video game does not inherently make those who play it violent, it will be up to the individual how he or she accepts such material.

You must also think about what context tarot cards are being applied in: is it presented in a good fashion; is it the center of the show, or just a characterization thrown in for good measure. If it shows the use of such things, such as divining, in a good light (ie: it promotes it and attempts to lure the viewer, vs. merely presenting it as a characteristic of a particular character or figure in the show), then it would be best to speak with someone on the matter.

Do not force her to 'stop' her anime watching, but if you so desire, counsel her on the dangers of preforming any art even vaguely tied to satanic lore (although that may not be the focus of what she is watching).