Silicone removal from bathtub ledge

My daughter, bless her heart, has removed a sliding door from her bath tub and scraped (as best she could) the silicone from the tub and surround, however, there remains a skim of silicone which I am sure will present problems in the future.

I followed up with a razor blade to scrape some more of the silicone off, but am still not happy with the results.

Is there a liquid which will remove the remainder of the silicone from the tub and surround which will not damage the surround?

Thanks.