A New Hampshire woman charged with lying to investigators about her whereabouts the day a University of New Hampshire student was killed is scheduled to enter a guilty plea and be sentenced next week. Prosecutors said Kathryn McDonough, 19, lied when she told investigators she had no contact with Elizabeth ‘‘Lizzi’’ Marriott, 19, of Westborough, Mass., on Oct. 9, the day they say Marriott was strangled or suffocated. Prosecutors said McDonough also gave a false alibi for herself and the man charged with killing Marriott, Seth Mazzaglia. McDonough is charged with witness tampering, hindering prosecution, and conspiracy to hinder prosecution. Marriott’s body has not been found.