I'd suggest that you not try to take away her iron.
She has the book, she's convinced that is is OK for women to sling around heavy iron - and now you want her to start with barbie-level body weight so she doesn't hurt herself.
Not saying you are not right about a deconditioned person - I'm just saying that psychologically it might not be your best move to push that on her. It could be badly received: she reads a book that empowers her and then you step in and suggest that she retreat to pink dbs. But then I don't know either of you.
Is she ultra-motivated to do this on her own and is deliberately not asking you for your opinion? Or is she asking you for suggestions on how much weight to use?
Many people here have decided to back off weight to work on form - but sometimes these decisions have to come from within rather than from without. Or from peers after a question (like here) rather than unsolicited from a mate. Not saying all women would react badly, but some women in some circumstances (like the unfamiliar free weight room).
Maybe suggest something fun like doing
B2B tabata squats with her at home on off days. Plenty of BW work, its only 4 mins and it's something that is new and additive rather than taking away what she's doing now. Just my $0.02