I have experienced mother-in-law issues before but not relted to confinement as my mom did my confinement for me at my place even thought my mother in law was living with me. I guess was worried about having to face the issues you are facing now.
In my opinion, i think you should speak to your hubby since it's really getting to you but dont't have to tell him everything. Just those that you think that your mother in law is being ridiculous about. For my case, initially when i started 'complaining' to my hubby, he always defended his mom but slowly he began to realise that his mom is a bit nuts. So drop hints here and there and they will realise the situation we as daughter-in-laws feel.
For now, just close two eyes and ignre her , afterall, 3 more weeks for your confinement then you won't have to face her everyday