If the offence she committed is classed as attempted murder or GBH, that might explain the severity of the sentence. Don't know if she left him bleeding profusely (Wayne Bobbit was minutes from death due to his severe bleeding), but that would aggravate the offence, too.
I've supervised female lifers who appealed against conviction and sentence because their spouse's violence to them provoked their attack. Appeals succeed where the woman has been able to show that attempts to escape have not worked, and/or enduring psychological harm has been inflicted from which they may never recover. If this woman can show this is what happened to her, her life sentence could be overturned.
I don't think cold-blooded FGM can be compared with the desperate crimes that some women commit following sustained abuse, but not in a position to know what motivated this woman. It would have a bearing on the outcome of her trial if was cold-blooded and planned, rather than an opportunity seized to prevent further abuse.