My MIL showers in front of her son (my husband)

I don't like this one bit and I told him today. It's not about me sexualizing it, it's about what is appropriate and what isn't. I'm American and he is French, and he said he grew up like that (the whole family being ok seeing each other naked, walking in on them while they shower, etc). At the moment we are in France visiting his family and staying with them. Today as my husband was finishing up in the bathroom grooming his beard, his mom walks in and she's like I want to shower. So she proceeds to take off her clothes and shower and my husband walks out. I told him it disturbs me and it isn't normal. What do you guys think? I don't like her to begin with (she's that typical MIL), and I put up with a lot of shit. But tbh I'm really put off by this.