The accusations came after she fell ill and was taken to hospital, meaning she missed her appearance on Saturday's X Factor and her contestant Andrea Faustini leaving the competition.
She was back for Sunday's final, but without her wedding ring.
Fans tweeted about apparent bruising on her face and scratches on her arms.
The X Factor announced on Saturday, that on doctor's advice, Mel B was told not to take part in the show.
Her husband Stephen Belafonte said that he found accusations that he had been "hitting" his wife, "disgusting and untrue".
So far there is no word from Mel B herself.
The couple married in secret in June 2007 in Las Vegas.
Ben Haenow was voted winner of this year's X Factor.
Tulisa Contostavlos replaced Mel B on Saturday's show.
On her return, the former Spice Girl thanked the medical staff who cared for her during her illness but didn't reveal what was wrong with her.
She said: "I really missed being here but thanks to all the doctors and nurses who took care of me and got me here tonight."
Asked by host Dermot O'Leary if she was feeling better, she replied: "Yes - ish."
There has been speculation that Mel B's chauffeur drove her to hospital after the singer suffered stomach pains on her way to X Factor rehearsals.
Her sister also posted a tweet asking for information.
She wrote: "This is ridiculous and cruel! Evil! How can NO one tell me and my family where my sister is and what is going on?
"Just a simple call to say she gonna be OK is all it takes!"
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Stephen Belafonte has taken to Twitter to deny online accusations that he physically abused his wife, X Factor judge Mel B.