The Dhammapada Commentary (DhA.iii.119ff) relates a ridiculous story about her misbehaviour with a dog in the bath house. Pasenadi was a witness of this scene, but she was able to convince him that it was the fault of the lighting of the bath house. Nevertheless, it is said that at the moment of her death she recollected this misdeed, and, as a result, was reborn in Avīci. The king was overcome by grief at Mallika’s death, and, after the funeral rites, went to the Buddha to ask where she had been reborn. The Buddha, not wishing him to know, caused the king to forget the question, every time he came to the vihāra, for a whole week, until Mallikā’s suffering in Avīci was over; then he allowed the question to be asked, and he was able to assure Pasenadi that she had been reborn in Tusita and to console him in his grief. It is said (A.iii.57) that Pasenadi was on a visit to the Buddha when a man came with the whispered message that the queen was dead. It was a terrible shock, “his shoulders drooped, his mouth fell, and he sat brooding, unable to speak.”
The sutta referred to is AN 5.49.