Can I retrofit ground to a two wire outlet from a nearby grounded outlet?
Retrofitting grounds is only allowed on old work.  For instance if you have an old circuit where you have already retrofitted ground, and you want to extend a new outlet off of it, you must use 12/2 w/ground cable. Meaning ground is included in the new cable. 

Yes, I don't see any problem tapping another circuit for that ground, so long as it's fed out of the same panel and the ground wire is equal or larger than is ordinarily required for this outlet.  

If you're just fitting an outlet where a switch or lamp was, then you can do that, provided you have the needed wires available.  You can continue using the ground you retrofitted.