Wait, was that an incandescent lightbulb? That baby monitor uses electricity. Does she unplug it when he's not in the shower? Typically it's cheaper (and healrhier) to make your own red sauce than buy jarred stuff. Disposable plates? Plastic silverware? That's an expensive hairdo and manicure, even if she does DIY.
In all my years of FIRE- motivated frugality, I have always practiced generosity of spirit by cooking for friends, making homemade gifts, lending a hand where needed, etc. It kept me from feeling deprived. Poor Stephanie has a lot to learn. I suspect (and hope) that her future self will cringe at her Scrooge-ish ways.
I'm not sure about how I feel about her partner. Methinks he knew what he was signing up for. Some people find life easier if someone else makes all their decisions for them.