I've tried date variations on her birthday but I can't seem to open the safe.
Any hints on how to solve this?
Her birth date isn't the date that's important here. Have you been to the library yet?
Note with dates: world variations can be important. 6 figure dates can be YYMMDD, YYDDMM, MMDDYY, DDMMYY....
At least a quick google search can tell you which variations are most common in the appropriate geographic area. ;D