How can I stop Google to revert to country extensions?

Its simple, let me help you, Type www.google.com/ncr and it will not redirect your country Specific URL land it will stick to www.google.com

Best practice is to bookmark or set your home page in your browser settings.

Let me know if you have any questions further.

Google Country Extensions

I think some of the previous answers are terrible responses and didn't help you out at all. and the one person who said that your sister should have worn an abaya makes me feel as if he's blaming your sister that she got harassed!! that's completley ridiculous, and in some Muslim countries women are supposed to cover up because the men say it's to keep them from getting harassed. well who's falut is it if the man decides to act on his impulses? the woman who is minding her own business or the man? this makes me sick! I'm sorry you didn't have a great time on your trip because of that incident. I think you should just let it go and realize that there are disgusting pervs out there that you can't really control. Peace and Love