Twixtor is made by re:Vision, who comply with the OFX standard, so it might well work. I'll give it a try:
I just installed Twixtor 5.15 in my Premiere Elements 11 VST plug-ins directory -- and they don't show up in the program. So either I didn't do it right or they dont' work with it.
I installed it into: Computer>OS(C:)>Program Files>Adobe>Adobe Premiere Elements 11>Plug-ins>en_US>editing modes and it works well. It is a bit finickey if you cut you clip before applying Twixtor. To get it to work well you have to export the clip as an mpeg and re-import it before applying Twixtor to it. This video is also very helpful as to how to use Twixtor in Premiere Pro, and it seems like the same interface in Elements. http://www.youtube.com/watch?v=cAxaiK4GrEY&list=LLpA0dx4OaXYdUcZPoyqBimg