could/might/may have done

A: "Where has your sister gone?"

B: "She could have gone swimming with some friends."

      "She may have gone swimming with some friends."

      "She might have gone swimming with some friends."

May I ask if those three sentence are all correct?   Thank you for taking your time helping me with my question.

Hi Viceidol

I would prefer may or might in your sentence.  In this context, I don't think could would would be my first choice unless more than one possibility were suggested, or unless the answer were preceded by something such as "I'm not sure":

A: "Where has your sister gone?"

B: "I'm not sure.  She could have gone swimming with some friends."

http://www.englishforums.com/English/CouldMayAndMight/dpdcd/post.htm