I have a request for this cake to be iced in buttercream (non crusting) with the silver piping and borders. She does not want the castle topper.  Any suggestions/tips? Thank you!

AYou need to post the picture, that's some sort of weird link.

Sorry - I'm trying! My main question would be how to create silver icing so it doesn't look gray? I also needs to be able to hold up on sides of cake without sliding down buttercream frosted cake. Thank you!

The only way to achieve shiny silver (not gray) is to pipe it in royal icing and then paint it with silver luster dust mixed with vodka. Since you're putting it on non crusting buttercream though, that could be a problem.  I can't see your picture so I have no idea what design you are using, but another option is to use fondant in the shapes you need, and paint them with silver luster dust. 

I have this same question, except I'm doing it in gold and on stabilized whipped cream not buttercream.

I wonder if you mixed piping gel with 24kt luster dust (or silver dust in the case of the OP), would this work?

This is the cake I've been asked to do