Sam, Glad to see that you arrived home safely. I'm also glad to read that she thanked your for her gifts. It's not unusual for the mlcer not to give the spouse anything.
If your gut is telling you that the ow may have spent time at your home, most likely she did. Was the home left the way you had left it?
As for her parents, blood is thicker than water and they will go along w/whatever their children are doing, even if they don't think it's right. Also, you don't know what she has told them about the situation.
The need to keep the affair secret is a bring thrill for them. It is excitement and a huge turn on for them if they think they are keeping something secret from the rest of the world. Once the affair is brought out into the light of day, the thrill is gone. You will find that many of the MLCers will act this way and will not file for a divorce. It's just the nature of the beast when it comes to MLC. She may not be sure that this OP is what she wants right now on a permanent basis.
Crazy people can try to make you crazy, paranoid and insecure, but you are the only one that has the power/control to not allow that to happen.
I seriously doubt that she thinks she's in MLC and I do not think that she is trying to mask her behaviors as MLC. I do think that she's got some serious issues and I also think that she's trying to push your buttons to get you to end the marriage. Texting is very impersonal and that way she doesn't not hear your voice nor see the emotions running across your face. It is very safe for them to use and not feel guilty when communicating w/you. Distance = safety and also keeps the guilt down to a minimum for her.
My advice would be to just leave her alone and focus on you and your pets. The new year is around the corner and you will have ample time to figure out what you want to do.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.