Well, I'd be teary and whiny too if I had to leave the beach after being there 6 weeks and I'm 10 times her age!

Grieving endings is a normal part of life. Support her in her grief as this is actually practice for other bigger losses we all experience as we get older. You can also help her build a bridge to her life back in the city. Are there things from the beach that she will still have back home? What is there to look forward to? etc.