Mother In Icu

My mother has told me several times in the past few years that she wanted to be a dnr. I have never questioned her, for it is her choice and I wouldn't want her making that choice for me if the situation was reversed. She had foot surgery about a month ago and was sent home with 5 pins in her foot. Everything was fine, or so I thought, up until a couple days ago. She was found on the floor of her apartment in a delirious state and I came and took her to the hospital. I stayed with her for a while, but she was agitated and kept arguing with me and taking things personal when I would tell her no or to stop, so I left and let the doctors argue with her. I went home and a few hours later I get a call from the hospital saying that she was very sick and was worsening quickly and was being taken to ICU. Her lungs were failing on top of the sepsis that she had developed from her foot, and she was having a heart attack. They then verified with me her dnr status and I reiterated that's what she wanted to be. They asked me several times and my answer never changed. So they said ok and put her on a bipap machine to help her breath and told me that she was worsening. I then drove back to the hospital and stayed in the room for a few hours. They asked me again about dnr and my answer did not change. Well I went home at some point and went to bed. I then wake up to a phone call from the icu. They told me that they had talked to my mom and talked her into changing her dnr status and that they were about to put her on a ventilator. I have no way of knowing if they did talk to her, if she was even in her right mind, or if they just kept asking until they heard what they wanted to hear. Now she has been on a ventilator for 3 days. They tried to ween her off of it today but she was not doing well enough. Furthermore she is/was awake for a good bit of it. She kept looking at me and moving her lips like she was trying to say something, and I can't help but think maybe this isn't something that she actually wanted. My mother is 58 years old and a heavy smoker. I'm not sure what I'm hoping to gain from this post, I guess I just want another opinion on the legality of the dnr. And what I should do in the coming days. Thank you.