i stayed in koh tao for 3 weeks as i couldnt bring my self to leave!
the island itself is quite cheap and the locals are very friendly however thats not to say they dont have crime.
the police force there isnt that great and i met a lot of people who has been burgled. plus i was constantly hearing tourists who had crashes but i think thats cause they were drinking and driving bikes. nothing happened while i was there a part from meeting a girl who had just had a bad experience with a local if you catch my drift?
the weather is nice there however sepends when you go, i was there whole of jan and it was sunshine with a few days of thunder/rain. however my cousin who was there is march time got caught up in the floods and the island was hit pretty badly. some months are just total rainfall but others are very nice. take a look at their rainy season to be on the safe side.
but is she stays in the main town and things i dont see why she wouldnt have total safety. im looking to go back there soon and stay for quite a few months, its on of my fav places on earth.