I don't think that she has used the word "quit" herself........ All she has done is said that this will be her last series, and OK, yes it's almost certain that she wouldn't have been signed up again next year, but all she is doing is telling us all that she hasn't been sacked or not given a new contract when the announcement is made next year.
Yes is jumping before she's pushed - but she has put the kibosh on any negative speculation about why she wasn't signed again - she's made it clear that she isn't looking to have her contract renewed.
I for one will miss her. She has done an amazing job most years on strictly, getting duffers a lot further than anyone thought they could..... Including one to a glitterball against all expectations, and despite the judges favouritism to other competitors. And let's not forget that she is one of the increasingly rare specimens of trained female ballroom dancers left in the show.
For what it's worth, I thing a few of the old guard won't be back next year..... I'm sure that Brendan and Anton will be retired, and Kristina won't get signed again..... Here's hoping that they will be replaced with real ballroom dancers like Oti, Gleb and Giovanni rather than the BTF brigade.