Kreia's motives for killing the Force are pretty well-established in the game. First, she's butthurt over being rejected by both the Jedi and Sith Orders - and no doubt her anger at this is amplified by how she has her own philosophies and teachings are are relatively unique, especially to the Jedi. Second, she somehow has it in her head that the Force controls everyone's fate in some sort of game of balance - and being a control freak, she can't stand that possibility.
Sure, from an in-universe perspective, killing the Force is an incredibly bad idea (assuming it would work) and Kreia has no actual evidence to support her second motive, but I figure that's kind of the point - she's evil. She's the main villain, remember? I know that Avellone has rather shamelessly stated that she's his primary mouthpiece for his own problems with the Star Wars universe, but that changes jack in the context of the story itself.
"There is something going on in time and space, and beyond time and space, which, whether we like it or not, spells duty." -Winston Churchill
"For of all sad words of tongue or pen, The saddest are these: 'It might have been!'" -John Whittier
"Apathy is death." -Kreia