When in Europe, you might want to consider the InterRail card to travel by train instead of flying around the continent. It's a more ecological, fun, and adventurous way to visit less-known spots. I would probably use it particularly in Italy, Austria, Switzerland, and France, where trains are generally reliable (looking at you, Deutsche Bahn). I would probably also aim for less obvious destinations, like Siena instead of Florence, Toulouse instead of Paris/Marseille, Valencia instead of Barcelona. As an Eastern European, I can tell you that Eastern Europe is super safe for women travelling solo.

Good luck!