How can we deal with a tricky person regarding our wedding reception?

we're getting married in october and are very happy together but a friend of his and aquaintance of mine is hampering after an invite to the reception and acting quite childish about it having sent a response (to an invite she hasn't received) saying she can't make it and nor can half of his family. I'm wanting to tell her we're sorry she can't make it to a party we hadn't invited her to yet so won't bother sending the invite (play her at her own game), but he's just ignoring it hoping it'll go away.