Hello everyone! I'm new, so go easy on me

We just got engaged on 9/11/09 and planning for a May 2010 wedding. We are starting to make our guest list and I need help with something!We are only inviting "and guest" or "plus one" if the couple has been dating a long time, are engaged, or are married. In doing this, we hope to avoid "randoms" at our wedding and avoid paying a bunch of money for people we don't even know.Here is my dilemma- I have a group of three girlfriends that I am extremely close with (we are all close with each other- not just me individually with each of them). Two are single, and one has a long-term boyfriend who I do not get along with at all. I know that going by our rules on who to invite, he should be invited, however I am wondering if I can get away with inviting just her since my other two girlfriends will be there alone and since she is very close with the two of them.Please let me know what you think! I appreciate the help in advance!