I was going to suggest you delete the Sim you don't care for, but I think you can just take her back into cas.fulleditmode and change what it is that troubles you. Give her new Traits, change out her likes and dislikes, whatever makes you not like her. Give her a chance. Or forever doom her to the Bin. I had a Sim I especially created for my Superstar in Sims3. They fell in love got engaged, and on Gift-Giving Day, right in front of his entire family, she openly and unabashedly flirted with Erik's only brother-in-law. His sister was newlywed, too. It was so shameful, I immediately exiled that Sim to the Bin. To this day, she's still there. Life sentence. LOL
