The file will never have higher quality than the 50% quality you exported.
You shouldn't have to import these low-quality JPGs into LR (nor would that help in any way). The original RAW photos should be in Lightroom, and you should work from that. In fact, Lightroom remembers your edits and so you should be able to produce an export from the RAW that meets the client's needs.
Thank you DJ_Paige for your quick reply!
How do I go about your suggestion? I keep the original RAW files in folders on a harddrive. I have the edited JPEG versions in folders on the desktop. If lightroom remembers the edits, where is this button once I bring the raws back up? I am sorry for the beginner questions, more details needed.....thanks a million!
In Lightroom, you go to the Library Module (click on Library), and your RAW photos with edits should be there.