Peoples primary hate for Sharon Osbourne is that she protects her own interests and by extension what she thinks Ozzy's best interests should be to a fault. Her job as his manager is to get him the best deals, and the most money possible and she goes about that in whatever way she can. She's very cutthroat about the whole deal. Then again maybe she's just taking after her father.
She's one of the reasons why Sabbath got together with Dio after they sacked Ozzy in the first place so that's not a bad thing. She's helped Ozzy through years of substance abuse, another good thing. She's survived cancer. Hell, she survived a murder attempt from Ozzy himself, and she STILL with him. She's very good at her job, but often times shes overzealous. She was behind the egging of Iron fucking Maiden at Ozzfest, that's beyond messed up. She replaced Bob Daisley and Lee Kerslake's recordings so as to avoid paying royalties.
As Ozzy's manager and wife she wields tremendous influence over anything he's involved in, and she'll be damned if Ozzy doesn't get as much as she can get for him, whatever it may take. If that means Ozzy's share is way more than Bill's that's not her problem and again it not her problem if Bill refuses to sign whatever percentage of the earnings is left either. You've gotta read between the lines a little bit.
But who knows maybe it was Tony and Geezer so used to getting a third of the earnings with a hired drummer ala Vinny Appice that they didn't want a smaller share either. The whole situation is messed up, no question, but there's nobody involved in this mess that's innocent.