Dow 's other film roles include the elderly lady who `` outs '' her grandson in `` Wedding Crashers '' , Disco Dottie in `` 54 '' , the recipient of Christopher Lloyd 's character 's slapstick in `` Radioland Murders '' and a choir member in `` Sister Act '' .
Other roles include the homophobic grandmother in `` Wedding Crashers '' , Disco Dottie in `` 54 '' , the recipient of Christopher Lloyd 's slapstick in `` Radioland Murders '' , and a choir member in `` Sister Act '' .