I have to admit, I laughed out loud when reading the update about the cable/gas connection. It was so asinine it was comical. I probably would have laughed in disbelief and said, Nice talking to you, see you later.
It sounds like somebody has been asking her husband if they could get a car, or something else major and has been told no, or that they can't afford it right now. And that very special somebody is taking it out on you and will continue to do so for awhile until she gets something to make you two "even" again, or it's apparent you just don't care about what she has to say. What a miserable person.
My advice is to just laugh, say "Good morning to you, too" or some other briefest-of-brief acknowledgements or completely ignore her. If she's not getting to you, she'll either stop or just get angrier. (If the latter, you're well within your rights to say that you weren't aware that your new car so compromised her quality of life, but now you do know, so she can stop sharing her thoughts. With a smile, of course!)
At playgroup, sounds like she has enough rope to hang herself. Just laugh it off and beandip to another mom. I'm sure you've been in the group long enough for others to know you're not a braggart and that the fellow group members are observant enough to see what a nutter this woman is.
Another E-Hellion behind you. Good luck!