Not about the NVL, but in your screen you are using Notepad++ for editing. It's been like a decade since I even touched Notepad++ but it's showing the dialogue text "with" and "return" highlight in blue... like it considers it code.
Are you sure you didn't add a regular line break at "... of her period,"?
In Atom and VSC that is exactly how it looks if you miss an opening or closing quote.
If that's just Notepad++ doing something funky, then disregard.
I agree you should increase your text box size to better match your dialogue.