As you know, she was way out of line to bring it up to you in the first place. She wasn't invited. You did not mention the event in front of her. It was not her place to come to you and say "Hey, I feel hurt."
Add to that how she has not invited you to her house, and yet still expects to be invited to things. She's a bully and she has double-standards. I wouldn't want a friend like that and you have also said you don't feel close to her.
I like a lot of the previous advice you've received.
Personally, I would say nothing to her. I wouldn't stress about inviting her and Felix next year. I'd be certain that I was not going to.
I definitely would not JADE because she's trying to bully you. It doesn't sound like she wants a fair, respectful give-and-take friendship with the airing of grievances and feelings. She just wants to be invited, wanted and included, and she doesn't want to reciprocate. I don't respect that.
Then, next year, when you invite your usual guest list, if you feel like it, you can say to each or some of the guests "These are the folks I'm inviting: A, B, C and D and no one else. Please, don't mention this event to anyone who is not A, B, C or D." You shouldn't have to do that, but it's still better than dealing with this.
If, next year, Monica has the audacity to say "Hey, when is your TG dinner?" You can just say "I'm not having it as I had originally thought" which is a vague way of saying "I'm not having a huge, informal shindig where you're invited" and leaving out the "I'm having a small, formal affair without you." Or you can find another way to deflect her question.
Ironically, I'm in a very similar situation. At a previous party, I had to tell one
loud-mouthed guest who likes to brag to others about being invited to things conspicuous guest that I was not inviting the X family. We're no longer close to the X family, they are similar to Monica and Felix as you have described them. I'm having a party tomorrow and have not invited the X family. This time, I didn't say anything to Conspicuous Braggy Guest about them not being on the guest list. If she mentioned the party to them, I don't really care. I don't intend to hurt their feelings, but I'm sick of bending over backwards to invite them to things, or not, and to spare their feelings when they don't give a darn about mine.
Sounds like you should just invite her to Festivus!
I was stressed the past two weeks in preparation for our party because my loud-mouthed guest and I used to be really good friends...back in my doormat days. Now that I no longer put up with her condescending put-downs, we're not as close. I was reading EHell and prepping myself with firm, yet polite replies to her common put-downs. I was not looking forward to my party specifically because she was going to be coming and I was preparing myself to defend myself every time she said something rude.
In the end, our family all got sick with the stomach flu and I had to call all guests and cancel the party so it never took place. Now, I know that like OP/sparksals, I need to just not invite guests to parties that I *used* to be friends with who I now find to be toxic and negative. Why have the party at all if you're dreading it?