The widow is Diana's mom and boy, is she one tough cookie. She's savvy, gritty, and has a lot of street smarts. Truth be told, she acts more like a business manager than a parent. In the play, she takes money from Helen in exchange for letting her daughter participate in the sleazy bed trick. (You know, the trick that involves Diana pretending she's willing to sleep with Bertram in order to trick him into having sex with Helen. That's not the sort of thing most moms want their kids getting mixed up in.)
Did we mention that the widow is also an Innkeeper? Yeah. The widow's business dealings sort of place her in Mistress Quickly territory, folks. (Mistress Quickly is the tavern keeper associated with prostitution in Henry IV Part 1 and its sequels.)
Shakespeare never directly accuses the widow of acting like the mistress of a brothel, but when Helen says, "take this purse of gold and let me buy your friendly help so far," (3.7.3), the widow jumps at the chance to make some money off her young daughter.
The odd thing is that the widow spends a lot of time trying to justify her actions. She and Helen insist over and over again that the bed trick is totally "lawful" (3.7.5), which makes us think that the widow knows her actions are kind of shady.