And, sadly, there are few other options. You can't really tell the search engines what to do. If you have the correct title on the page now, then you've basically done what you can do. The search engines will choose to display whatever they want, and will update -- if they update -- on their own schedule. (Google, for instance, has been known to display their own idea of what the page title "should" be, without regard to what title the webmaster entered.)
With any luck, Bing will notice before too long that your page title has changed and update accordingly. In the meantime, your only other option would be to remove the sitelink (assuming Bing has that option -- like Jill, I haven't spent much time exploring their Webmaster Tools options).