Sam's mom is crazy

So I started watching this show and can I say what a good show so far. The characters are refreshing, funny, cheerful kinda resembles with reality. However, I am just hating Sam's mom at this point. How can a mother remain angry for that long. How can a mother just ignore her child like that and cause so much pain to her child. I understand she lost a child she loved, but Sam is also your child lady. You can be angry and blame her but not for so many bloody years.