If you miss your ovulation (i.e. are unable to be inseminated because you are away), it is not possible to ovulate again during the same cycle. Your friend must not have had her information correct.
As to cancelling your vacation - the real question is whether it is more important to you to try to conceive this cycle or to go on vacation. Vacation is often a good opportunity to relax and start with a fresh cycle the next month... either option makes sense to me :-)
Good luck!
Rachel Inbar
www.FertilityStories.com
