You think you could be good friends if you met her some day, there is some thing that gives you this impression that you would click so easily but meeting people is like a chain of accidents and then it's just a matter of choosing to make and stay friends with or not but in this case that's a shame that you never met each other.
There is time that you feel you could be good friends if you met the person under other circumstances. If only your title was a classmate, a co-worker, a stranger or friend of a friend. Then you two could be friends and not just relative which you are. Especially with this imposed and to some extent unpleasant clichéd title. The relationship is "unfortunately" defined in one word: Distance.
You feel a bitter interaction, a negative energy in between which some prefer to name, maybe it's the chemistry that is not right, whatever that is you feel like you're the only one walking and on a one way direction and you think it would never work whether you met this person under the sweetest circumstances or as a relative who wouldn't carry any repelling title or would carry one. This relationship is "always" defined in one word: Distance.