Reeby/Reebey, Reys, [name]Aby[/name] or any others? Are all of these too much of a stretch?
[name]Abby[/name] can work. Reys it fine. Reeybey isn’t a nice name imo.
[name]Aurie[/name] is one, Reeree/Riri, Reya, Breya.
[name]Aubrey[/name] is most likely to be called Aub or [name]Bre[/name] and I think they’re both great! I like [name]Aby[/name] and [name]Ree[/name] as well.
I named my daughter [name]Gabrielle[/name] because of the many great nickname options…thinking I’d call her [name]Elle[/name]. But, of course, she’s now normally called [name]Gabi[/name]. She’s still young so things could change. 
I think they’re all a little odd as nicknames for [name]Aubrey[/name]. Why not just call her [name]Aubrey[/name]?