Is it her first time traveling alone? Where is she headed for?
Apart from Africa, I think most places should be safe for a solo
female as long as she is independent, has a good sense of
direction.
Just get her to bring 2 cell phones, one spare another one carry
with her wherever she goes. If she doesn't deck herself in loud /
revealing clothes, be conservative, don't wear flashy accessories,
don't carry expensive stuff, dull colored clothing, no make up,
look messy, look poor, don't linger in a single spot by herself for
too long, pick up a foreign language book, why would she get into
trouble?
Be supportive lah.