The SketchUp team has no control over third party extension developers, so you need to contact them, or get help from other users, which was why I pinged @NiCa60 …
But maybe he might not be involved with this user forum, anymore.
In addition to the conflict issue, some extensions require compiling, which doesn’t work out of the box on Windows because there is no default system compiler to do so, and you cannot expect end users to have this available.
You could try to install it in your local system Ruby installation, Then copy the gem into your extension. (Installing ruby gems in Sketchup) That would be ok for your own usage. But, if you plan to distribute it I would recommend you fork the gem and wrap it in your own namespace, then build and bundle it into your extension’s namespace.
That way you avoid clashing with other extensions (requirement to be listed on Extension Warehouse). And you avoid the potential gem install/Gem.install issues on user’s machine. (Might fail due to expired SSL certs on older SU versions. Freezes SketchUp for the duration of the gem installation.)
Ok. First, everything Thomas said. Extension gems are almost impossible to use in a ‘generic plugin’ for public use. Conversely, if you need it for a controlled ‘local users’ application where you can perform additional setup steps, one should be able to use anything that can be used with stand-alone Ruby.
That said, this may not be trivial. Also, at present, I don’t have (or need) SketchUp, although I’ve used it in the past. Conversely, many would consider me a ‘knowledgeable windows Ruby user’.
How did you install the gem in SketchUp? Are you sure that’s correct?
If you’re not sure about 2, using the --user-install option should make it available in SketchUp, but that depends on how Trimble setup Ruby. If the value of Gem.user_dir matches in both stand-alone Ruby and SketchUp Ruby, it can be used as a common gem install location.