Green’s Dictionary of Slang

(US campus) excellent, first-rate; of a person, attractive.

1962		Eng. Journal LI 323: Both bitchin’ and cher (with variant cherry) are relatively harmless today, equivalent to neat or swell, but both have meliorated from less innocent meanings [HDAS].
1984		Eble Campus Sl. Mar. 2: cher – expression of assent and approval [...] She sure is pretty, isn’t she? Oh, cher!
2003		McGill Reed Dict. of N.Z. Sl. 45: cher bro Excellent, to a contemporary teenager.