Hi Scattered ,
Welcome to the forum .
A couple of observations ; though the pictures you have submitted are kinda fuzzy and we would also love to see the ukiran (handle) .
I'm going to take a wild guess and say that the pamor or pattern on the blade looks like wos wutah (scattered or strewn rice grains) which is a beneficial pamor pattern aka 'friendly' .
I'll go out on a limb and say that this is not an 'evil' keris .
The cross piece on the scabbard is of the gayaman form which is considered informal . Hard to tell about the pendok (metal sleeve on the scabbard) but I'm willing to guess that it is fairly new .
I think we'd all like to see some better pictures of the entire piece .
Now I'm thinking that if your Sis bought this from a palace guard it is most likely not the first one he has sold to visitors from other lands .
I think you'll find that there is always a story that accompanies every keris sold in Jawa . the idea is to purchase the keris rather than the story .
From what I can see (from the pictures) it looks like an average keris in quality ; age is hard to determine from photos .
Whatever it cost the money has been spent and at this point is of no account . The real question is whether you like it or not ; if you do then it was worth the price .
I hope you'll stick around and learn a little more about these fascinating cultural icons .
Best
Rick