I was in Lima for a week 2 years ago with two other friends we were 23 all males but we found Lima very safe. We felt safer on the Subway than in some parts of the US and the UK! We walked around the city many times and never had a problem. We went through one unfriendly area that I would not like to push my luck by walking through there again but all cities in the world have these areas.

I think you should let your daughter go. If she is in a group I am sure they will be well looked after and it would be a fantastic opportunity.