Thanks everyone for your replies. I tried to respond to all the great suggestions. Your comments made it more clear to me, what kind of person I think I'm dealing with. Sorry it became so lengthy. This also helped me to see it more clearly by actually writing it down. I did highlight the more important things in case you don’t want to read it all.
I do remember being sleep deprived at times when my kids were babies but I would have never, ever considered yelling at them. Babies cry. My girlfriend had a colicky baby & I really empathized with her. This is not the case here, the baby is not colicky. Before the abuse started this little girl didn’t cry much and if she did, it wasn’t for very long and it never bothered me, I would just go back to sleep. She just cries, and only screams when the mother comes in yelling at her. I don’t understand why the mother responds so quickly to her when she does cry. I truly feel that the mother is just a very self-centred person, who never learned how to raise children. Maybe she had very poor role models. Last week she was walking the baby down the hall. She mentioned that the baby always sleeps during the afternoon, so during this time the mother could have a nap herself. She, unlike a lot of mothers, doesn’t work, and it really doesn’t take a long time to clean an apartment. So I can’t see the problem being that the mother could be tired or sleep deprived. As for offering to babysit (which is a great idea) I don’t have the time since I work & go to school. By evening I’m just too tired. (I’m sure a lot more tired than this mother) The grandparents come on a regular basis, and I believe that they have taken the baby. Another thing has concerned me in the past. She may have left the baby alone, but I don’t know for sure, just a feeling. A few months after my concern I met her downstairs ( both of us coming home) and she made the comment that someone was watching the baby, that she wasn’t alone. I thought this was such a strange comment. Most people assume that a baby wouldn’t be left alone and I had the feeling that she was covering herself for times when she may have left the baby alone. Since the banging on the wall incident I haven’t heard the mother yelling. The last couple of nights, the baby predictably wakes up and cries for a couple of minutes and goes back to sleep. Maybe I scared this mother, but I believe that it will start up again eventually. I am very concerned that it could escalate to physical abuse, especially when the baby gets older and more verbal, talking back, mimicking the mothers behaviour, etc. which may happen. (or she could become a very scared passive girl) I did confide in the neighbour that lives below this mothers apartment. This lady is a retired nurse. She hasn’t heard a thing. My bedroom is the only one adjacent to the baby’s room. I am very concerned that if I do talk to the mother that it could escalate. If she is self-centred like I believe, she may resent the baby because she was found out. I don’t get the impression that she has post-partum depression, but I don’t know enough about it. I would think that if she suffered from it, it would have happened earlier on when the baby was an infant. I’m sure that it was a very stressful time when the baby had heart surgery as an infant. But most mothers reactions would be to over coddle an infant, not down the road abuse her.
I really appreciate the Govt info Skully. I’m going to look into the Healthy Babies, Healthy Children program. Never mind what the child is going through, I really hate the position I’m in. I’m not a nosey person and for the most part don’t know the goings on in this building. I just can’t imagine when someone knows about abuse that they could ignore it. I could not live with myself, knowing that I could have stopped mental abuse, especially if it escalated to physical abuse. I do think that I will go to her with a letter, in a friendly way, that I'm concerned for both of them. That way I will say what needs to be said, she can read it on her own. It doesn’t seem as confrontational that way. If I talk to her, I’m worried that it could get out of hand and that things may be said that could make things worse. I will give her some phone numbers and a copy of the Government Info that Skully mentioned. I have to admit that I’ll be scared when I do go to her, but I know that it has to be done. If her reaction is very negative or if I hear of any more abuse I will have no choice but to report her. Thanks again.