A 'net search on "Hyrel" didn't really reveal anything of significance. However, your telling us that this is a name of possible German origin proved helpful.
While I couldn't find any exact spelling of the name "Hyrel" listed among any German reference resources, I did take into consideration the fact that many names undergo spelling transitions over time and distance (as in immigration to new countries), and then one must employ the use of Soundex to come up with a likely "hit" on an unusual name.
I therefore found this website describing the origin of the German name "Herl":http://www.gschweng.de/herl.htm
A translation reveals that, in Austria, this name took the form of "Hierl", which is bringing us closer to your "Hyrel".
The name apparently corresponds to the names "Gerlach" and "Gerold", which mean "spear tournament" and "spear wielder" respectively.
Taking an educated guess, I would say that your friend's great-aunt may have been given a German/Austrian surname such as "Hierl" as her first name, and that here in the U.S. (which is where I see you're posting from), that name was changed into "Hyrel".
So you can probably tell your friend that her daughter's name may be related to "Geraldine" (via "Gerl", via "Hierl"), and that it possibly means: "spear wielder".