Green’s Dictionary of Slang

sentimental.

1885		Nat. Police Gaz. (NY) 19 Dec. 2/3: When a first-row bald-head develops into a dramatic critic his efforts are necessarily slushy.
1892		Derby Mercury 31 Aug. 6/2: American Murderers and ‘Slushy Sentimentality.’ Sentimental sympathy for murderers is pretty rife [...] brutal murders are glorified in headlines as ‘nervy’ and ‘cool’.
1911		E. Ferber Dawn O’Hara (1925) 27: No more slushy Sunday specials! No more teary tales!
1915		Daily Trib. (Bismarck, ND) 21 Apr. 11/1: [He] peddles his pet line of slushy gush.
1929		Eve. Teleg. (Angus, Scot.) 28 Jan. 4/3: [headline] Slushy Hymns Sung To-Day.
1955		J.W. Ellison I’m Owen Harrison Harding 184: Movies like that are slushy and silly.
1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 112: No, they’re not all slushy romantic novels.