Mrs Leech

In the novel Death on the Nile, Mrs Leech is an acquaintance of Mrs Allerton and her son, whom she met in Mallorca.

She lost her ruby ring, and wanted Tim to accompany her to the police, since he spoke Spanish. She believed her ring had been stolen, but Tim claimed she must have lost it while bathing in the sea.

Given Tim’s background it’s not unlikely that he stole the ring.