If you are talking about the Solo cups, no you are not over reacting. I was in the EC one night and a beagle was brought in bleeding out from eating a plastic water bottle.
It was horribly sad. Hard plastic can cut their GI tract.
Sounds like poor Anne is not being well cared for. The problem in TX is that the laws are not so great...if a pup has shelter and water that is about all that anyone cares about.
You could call animal control for some advice though...I have always found the ACs to be very informative. I am sorry you have to watch this...very hard to see an animal not getting good care.
If you have a decent relationship with your neighbors, why not just go talk with them?
I would simply call the AC for advice...and then decide what to do. Good luck!