How is it traveling alone in Bangkok and Ho Chi Minh City?

I am a girl, and I planned to travel with a girlfriend and now we seem to have too many differences in opinion. I am the more adventurous type and she wants to stay in nice hotels and fly everywhere. I am considering traveling alone so we don't ruin our friendship ( I know...should have talked more before buying tickets). How safe is it for me to travel alone in these two cities?