Slim wasn't upset when Lennie killed Curley's wife he was really worried for Lennie cause Curly would want to shoot Lennie for even going near his wife. Slim was also worried for George because Curly might think that it's also a part of George's fault for bringing him there with him. When Lenny killed Curlys wife Curly was very upset and said he was going to shoot Lennie because he wants the power of killing Lennie instead of someone else killing him.
In summary of the book “Of Mice and Men” Lennie had to depend on George for everything. George and Lennie lost so many jobs because Lennie does not know how to control himself.Lennie did not purposely kill Curlys wife in a way it was Curlys wife's fault because she wouldn't leave him alone and she kept bothering him. Slim was not upset with Lennie he was more worried for Georges job because Curlys dad might think that George had something to do with the whole thing. Do you think Lennie deserved to be treated the way that he got