Because she's your dad's friend's sister and, I assume a rather large age difference, I understand your fear of pursuing a relationship with her. The fact that she just broke it off with her ex does not necessarily mean that you could be next in line. Being her friend is one thing, but moving it to another level may not be available to you. In order for you to take a chance on this, you'd have to not care what your father thought about it, and you'd have to be ready to be turned down and risk losing the friendship. The age difference, alone, could be reason enough to take a pass. Older woman/ younger men relationships are often fleeting.