I'm sorry. I have had in law issues in the past, then I realized I was being overly judgemental about things. They did some things that really really irritated me and we saw a lot of things differently. My husband and I also had t go to counseling to help with this, as it was a main concern in my marraige and he was also fiercly loyal to them and always sided with them.
In any case, we have an absolutely wonderful relationship now. I've put things in teh past and we've talked about some issues, but most of the things I got pissed about then, I think about today and laugh because it was so silly.
I agree, there are some safety issues, but they really aren't that bad. Are they very attentive with your son or do they ignore him if he were to fall or injure himself? You have to remember the parents of the older generation were much more lenient with safety precautions, we are a coddled generation who are hyper-sensitive to safety concerns, so try and pass that off as a generational thing. If it still bothers you, then don't let her watch your child unattended. Let her know point-blank what the safety concerns are and that you stand by them. just be sure not to nit-pick. I know it's easy to find fault on people who annoy you, but really if yo can get past this, you may see it's really not that bad.
As for the sleeping over, just tell her you aren't comfortable with him doing that at this age, but maybe in a year or two when he is a little more stable with walking and climbing, once or twice a month would be fine, and let her have a few days a month to really spend some quality time with him. Or, tell her up front that if she can remove the swivel chairs/ladder from her front room, then it would be okay so you would know that those won't be issues.
Also, encourage activities with her and your family, at your house, at the zoo, at the library or movies, or out to dinner. It's helpful to get out and do things that are enjoyable so oyu won't be feeling pressured to watch her every move.
Really, sharing a therapist would not be a good thing, but it sounds as if your therapist already knows that which is why he/she has referred your mil to someone else.
Aside from her contacting your therapist, I really don't think she sounds all that bad, and she doesnt' sound nuts either. When I was pregnant I always got more upset and super emotional about people that annoyed me as well, so I wonder if that has anything to do with some of the things you are seeing? I'm wondering if you are riling yourself up over her and getting angrier and angrier by the minute on issues that are really not all that bad. I speak from experience here.
Kade gave wonderful advice, I especially agree with what she said about how she may be pushing harder to get close b/c she can sense you pushing her away.