One of their founding sisters could have had a bio sister or friend who was an A Xi D, or they could have started out wanting to go A Xi D national but never did. Unless they are only a couple years old, by this time that part of their founding is probably not even thought about anymore. One of our chapters started out as Zeta Tau and their colors were light blue and gray (sound familiar Barbara?

) probably because they had friends or sisters who were Zetas or wanted to go that way but they went ASA.
Also, I was surprised to find out about Alpha Sigma (a local sorority at UW Whitewater) whose colors are the same as ASA's - my first thought was "copycats!" Boy, did I have egg on my face when I found out they were founded in 1899 - 2 years before we were!!
In all honesty I wouldn't worry about it. There are only so many colors, mascots etc that are suitable to use (and there are LOTS of groups that use shades of blue and gold) and a lot of crests have similarities (Kappa Delta and APO have some identical imagery in theirs). Unless they are representing themselves as an A Xi D chapter, I doubt there's much that could be done.