Going thru a divorce and a family wedding...?

My friend Ron has been seperated from his wife since december, Rons nephew announced in Feb he is geting married this July. Invites were sent out to Rons new address and one to the soon to be ex (Hilda) whom nobody really likes and she has no love loss for them either. anyways, Hilda rsvp'd at the last minute..she didnt go to the shower she didnt send a gift, She knows Ron has a girl friend, the whole family does and she is invited also. So is Hilda doing this to be spiteful (GF didnt cause breakup) SHould the nephew un-invite her because Hilda filed for divorce in april with very nasty accusations about Ron. Its not friendly at all. Rons GF isnt going she dont want any trouble. Family didnt think Hilda would come and really still thinks she is just stirring the pot.... BUT if she goes and Ron is there isnt that wrong in the middle of a nasty divorce? She has no family ties anymore can she tell her lawyer they went as a couple? what will that do?? can this mess up his divorce? (michigan).