Pissed and wondering how to react

Hello friends,

I come before you with a friend problem which am not sure how to proceed.

I have this friend A, as couples we were close initially but not anymore. Partly it is years growing apart and get involve with kids own activities but partly it is also I noticed she is drawing away. Eg, if A have function or party we wd always go full family, stay the whole time talk nicely etc but not reciprocated by them at our getogethers. A will send hubby only or or come v. late, wait for few minutes and leave early etc. Basically just for name's sake. initially was hurt but accepted it then I also got fed up. So I also stopped going. now they dont invite I dont invite. I mentally written off this friend couple. Ok?
So far so good.
now problem is I run into her FIL while outside recently and he mention oh troubledmom where are you we dont see you these days at all etc? I just and mutter oh we are busy etc. He mention next day they have party in A's house and you are coming no? Actually I not invited that function. I feel embarassed to say that and say No I dont know about their function and wish him festival greetings and get out of that place. I feel embarassed to say to his face A didnt invite me to function so I am not coming ur place ok? How can I say say that? I feel it is too rude. But it is the fact. but this man go on and on oh where are you these days, we dont see you etc every time whenever I run into him casually. I only nod and smile.
Now few weeks later another mutual friend also come and ask me what happened? that this A was asking her about me, was telling her at party we dont see Troubledmom where is she? etc. Isnt this heights? A wd not invite me to her party and now she telling ppl at her party I'm not coming to her house and she dont know why? She very well knows she didnt invite me that is why I am not going there, so how she can lie like this? Again I dont know how to react. I dont want to say about no invitation becos this one will tell to that one and it will become issue. I am not begging for invite to their place. I dont care. I dont want to go there only. Why should I go when Im not invited? I like this no invite policy. But I dont know how to answer these 3rd party people who are asking innocently why I am not at this person's house. I dont know why this A tell lies like this when she very well knows she 's not invited me. What to do? How to deal this gracefully and casually and close this chapter friends? Pls give ur advice.