It's her name and she trades on it. They want to trade on her name without compensating her or giving her review of the product (potentially damaging her brand). Moreover, they're implying she endorses them while she has done no such thing. How is this hard to grasp?

As far as licensing actual words (since you want to separate "swift", the word that means quick and agile, from "Taylor Swift," the pop icon the brand is trying to monetise), consider Word, Excel, and Windows having been trademarked by Microsoft for decades. There are many others. Of course, you can use Excel, but you can't use it in spreadsheets. So while the "Swift Home" company isn't making music, the fact that they're using her name and arguably, the way she distinctly writes the S (which I don't agree with) is what she's taking issue with.