I DOUBT THAT Miss Jane Marple or Miss Hildegarde Withers would approve wholeheartedly, but Mrs. Wagstaff, appearing in Sylvia Angus' Dead to Rites (Crown, $7.95), has made a forceful bid to join their circle. The elderly busybody female sleuth has been an appealing character since the 19th century when Anna Katharine Green began writing her stories about the "meddlesome old maid," Miss Amelia Butterworth. True, the widowed Mrs. Wagstaff is not a spinster, but she shares many traits with her sister snoop - and intrusive curiosity that could be called nosiness, an independent spirit, shrewdness about people, and abundant eccentricities.

Mrs. Wagstaff, a salty, robust woman with an ample bosom and a Roman nose, makes her entry against an exotic background of Mayan ruins. On a bus tour of Mexico, on of her fellow passengers is more interested in men than archeology - that is until her body is found floating in the sacred pool of the virgins. It takes Mrs. Wagstaff, who usually solves the mystery novels she reads by the second chapter, to puncture the theory that the killer is a 20th-century Mayan fanatic. One drawback is an excess of cuteness as the authors strains for humor.Mrs. Wagstaff should put her foot down.

Another variation of the amateur female sleuth is the nurse in The Murder Cure (Avon, $1.50). Ann B. Ross has come up with a heroine who breaks the mold and emerges as an individual character. Amy Boland, a nurse who has put her husband through medical school (only to wind up divorced from him, and not without emotional scars) is supervisor of the emergency room in the Charleston County Hospital when another nurse is found brutally murdered. Amy is gutsy, and she doesn't fall into the arms of a rescuer who uses her as bait to catch the murderer. Ross writes convincingly, although the killer won't fool the reader as long as he does Amy.