Semarang is a very safe place to stay as a woman, I was never bothered by any people during my stay, people often ask for pictures with you but nothing more :) I do recommend not going out late at night and always tell someone where you are and what you are doing just for more safety

Generally it's safe The problem is the weather Really hot and humid there. Better get your spf ready because the sun is really harsh. But be careful, don't play with your mobile phone at the quiet streets. Sometimes people will steal it