are we reading the same manga here ? because the attempt of you whitewash Tsubaki action is insane.
The owner lady of the brothel or something, clearly said to her they gonna wring "every last cent out of them", and she was gonna doing so with Ayano too. and Tsubaki are still doing said job with no sign of her redeem yet.
And with the work experience and seduce skill, they know how to trick and manipulate people in. Look at how she purposely seduce and grooming Ayano. manipulate in play, especially using love and affection and trust, with ill intend to drain that woman of her money. At best they didn't do it illegal, but for sure scummy.
To you, that woman is a disposable character so you don't care what she going through, you only feel bad for Tsubaki, she is born into this and don't know better and groom into this life. Yes what about that poor woman who got tricked by her ? if Ayano going through the same thing and her family is destroyed, which is what they planed to do here, you also gonna say it is fair and it is Ayano fault, no one force her ?
While we could expect she actually fall grow to care for Ayano for real and don't do it cliché scenario, That woman unfortunately is not that lucky.
and you could also agure that woman also did nothing wrong. What she said is true, she is a prostitute, reason to called her, even if they not knowing each other, surely acceptable and agree by everyone have Tsubaki not left and the show go on.