Should i make a move on her? Men and women..?

No, you don't have to explain to her sister why you didn't speak to her when she came in previously. Just be nice and say "hello" the next time you see her. As for hitting on your boss - DON'T DO IT!! That can lead to you losing your job. Have you ever heard the phrase, "Don't crap where you eat"? That means don't date people at work because it can turn out badly and make for a very awkward situation down the road. If you value your job, then stay away from your boss. This may not be what you want to hear, but I've been around a while and I've seen people date people at work and it never turned out good. Managers shouldn't be dating their employees anyway and alot of companies have a rule against it.