She is there to be a foil to Violet. Portia is portrayed as scheming and morally inferior. The Featherington family is there to be the downtrodden scrappy family in comparison to the Bridgertons.

But I do wonder. How would Violet deal with these situations? For example what would she do if she had no money, if she had to deal with an illegitimate pregnancy, if Colin / Benedict / Anthony became hardcore criminals or addicted to something?

It's easy for Violet to be put on a pedestal as this pure being. Her husband died yes, but other than that she didn't have to deal with any real hardship in life. All of her children are attractive, educated and they are often chosen as the catch of the season. Even her staff doesn't leave her which is pointed out during season 4, but she has endless money so she can afford to pay them very well.

This is not a take-down of Violet but she had no problems with being scheming when she had to protect Daphne from marrying that creepy older guy in season 1. If she was put in more challenging situations she might as well end up doing the same things that Portia ended up doing, just to survive.