sorry to burst your bubble buttlover, but 4th map doesnt drop sabrina.
@yoxal there are level recommendations before the start the event map, like req lvl 1 units, 25, 50, cc25 (X tier), cc50 (G-tier).
for the most part, those recommended levels pretty much work. most of the time you SHOULD aim for having higher level units though. also finding some guide videos online would help.