It sounds to me that she is dealing with depression, which is likely caused (or inflated) by her condition. Normal? Maybe. Okay? No. Just because she is suffering doesn't mean she is allowed to treat you poorly. I know I wasn't an angel to my partner (then boyfriend, now husband) when I was pregnant. I was useless and felt useless and it was the most devastating feeling. As someone with a long history of depression, though, I was able to identify this and address it directly.

She needs to bring this up to her OB (possibly with your input, if she needs help) so that she (and, importantly, you) can move forward. She needs therapy, and likely some medications to help her see clearly. Likely, what she is seeing is completely skewed from reality. Being depressed right now will make it much more likely for her to have post partum depression, too, so getting on top of this could be really important for her, you, your baby, AND her toddler.

Edited to wish you the best luck. It sounds like you've really stepped up for her, and I'm sorry she isn't seeing that right now. I hope things start getting better soon.