Well that paragraph is very well written in my opinion. There are one or two minor errors with punctuation, I'll let you figure that out for yourself.
If I recall, Lenny actually feels Curley's wife's hair, as well as her dress. She screams and it goes on...
If you have not already written, you may want to consider including that in George's defense, George kills Lenny out of compassion, before the other mean at the ranch have the opportunity to kill him, where they would do much more brutal things than shoot him. We're talking about being string up, stoned etc.. A rough time in history.
Although in these times, women had little rights, they still had some and if a man raped a woman there would be serious consequences as I'm sure you're aware.
In your paragraph, you write "Of course you would be upset. This is rape." It would be better to use and ellipsis here, to build suspence to a valuable point.
You also talk about a mental asylum for Lenny. There would be no such thing as we are talking about the late 1800's, so this sort of healthcare in the US particularly would have been a luxury and not for working class, again backing up the point that what George did was an act of kindness to prevent any to further mishaps occurring.
Hope this helps.
Most people seem to hate Of Mice and Men, but in my opinion it is a great play. My favourite in which we have studied.