It follows an injury that occurred last Friday, forcing her to alter her main routine.
The singer then ended up in the dance off but with the injury worsened, it was decided she could not perform.
As a result, the elimination decision between Anastacia and Melvin Odoom reverted to the public vote. With the fewest votes, Melvin was eliminated.
The cancelled dance off was a Strictly first and the choice had plenty of critics.
But unfortunately for Melvin he is out of the running and tonight Anastacia is still set to perform.
She's been given the all clear to dance by doctors however the pair will have to again reduce their routine to work around Anastacia's injury.
The singer explained on Sunday's show how she had ripped scar tissue on her chest from a double mastectomy.
A spokesperson for Anastacia said in a statement: "[On Monday], Anastacia visited the clinic of a specialist in breast reconstruction surgery. The doctor again confirmed that there was a tear in the scar tissue, which although painful is not permanent.
"She was given the all-clear to dance this weekend with the caveat that the routine is carefully choreographed and she has been given the appropriate medication. Brendan was with her for her appointments and they have been filmed for this weekend's episode.
"The specialist will be monitoring her condition regularly, and she will revisit them on Monday.
"She is doing this to raise money for breast cancer, so unless a doctor tells her she can't carry on, quitting would never be an option. Anastacia and Brendan are now in rehearsal."
A rep for the BBC added: "Anastacia is rehearsing her Viennese Waltz and is planning to perform it with Brendan on the show this Saturday."
On It Takes Two last night, Brendan said: “She is alright for tomorrow, she’s looking really good actually."
This weekend will see Strictly head to the movies with the first theme week of the series.
Strictly Come Dancing continues tonight, live on BBC One from 6:45PM.