She didn't have much of a career left by the time she married Redknapp and had kids. She was in an indifferent girl group, then went solo after they fell out, but the solo career was based on cover versions and a tour sponsored by Soft & Gentle deodorant so really wasn't going to go anywhere.
Even after her marriage she hardly dropped out of the spotlight: she and her husband regularly appeared in adverts and she gave many, many interviews to magazines about being a mother and how important family life was to her, etc. etc. I've got a sense that she may even have endorsed a range of baby clothes or written a book on parenting or something. In other words, she was following the Myleene Klass/Jools Oliver 'I still want to be famous but I'm not on telly much so I'd better be a professional famous mummy' strategy.
I suspect it's the old 'can't bear not to be famous any more' story. She puts me in mind of the appalling Emma Bunton actually. Look at meeee! I'm still here, everybody! I'm not going away!!
Louise undoubtedly campaigned to be on Strictly - I don't believe for a second that she was approached previously and turned the show down - and decided to use it as a way back into being a bit famous again, in this case in a touring production of Cabaret. Her agent has probably decided to present it as 'poor downtrodden woman breaks free, isn't she courageous, look, women, here's a celebrity you can get behind if you've got £35 for a ticket, go and see Cabaret NOW!', but I'm not buying the story that her glittering career was curtailed by marriage and her selfless devotion to her family.
This sort of thing cheapens the experience of women who are really downtrodden in their relationships.