I believe you have Lightroom CC installed. Assuming you actually have a serial number for Lightroom 6 you can convert CC to 6 by reading this: Adobe Photoshop Lightroom Help | Serialize Lightroom CC trial to activate as Lightroom 6.
This won't change any speed issues the user might be having.
She may be having speed issues because the face recognition feature is turned on, or it may help to turn off the GPU acceleration, or possibly a dozen other things might be happening.
maureena23249087, exactly what is slow in Lightroom?
True enough but I have no idea why the OP is referring to a "mobile" version of Lightroom on the desktop. There is no such thing.