Wendy Williams will remain locked up indefinitely, but she got good news Friday ... a judge will allow her to fly to Miami for her father's 94th birthday.

Sources with direct knowledge tell TMZ ... the judge has authorized private security to accompany Wendy from NYC to Miami, where her dad will celebrating with friends and family. Wendy will be there for 2 days and then fly back to NY ... where she is confined in a studio apartment at an assisted living facility.

TMZ has interviewed Wendy for a new Tubi documentary -- "Saving Wendy" -- and in it, we raise serious questions about why she is still in a guardianship that gives her virtually no freedom. She calls her apartment a "luxury prison," where she rarely gets to breathe fresh air, has no internet access, and virtually no visitors ... no one can even call her.

We've also learned the judge is prohibiting Wendy from having any further contact with the media.