Mavis Trouncer
Little is known of her except that at some point in their respective pasts, she and Samuel Vimes made an impact on each other. Evidently this is not a memory Vimes likes to revisit, as whenever he is in one of those near-Death experiences where his whole life flashes before his eyes, he hopes and prays it fast-forwards through the bits about Mavis.
Is this the woman who according to Fred Colon "brung him low and gave him the nudge over the brink into outright alcoholism?