Should I tell my bestfriend the truth?

(Pardon me for my grammar) My friend and her BF got into a bus accident few months ago, the cause was the truck collided with the bus. Her boyfriend Jacob died along with the majority of the passengers. Only My bestfriend, Mae and three other people survived. According to the people who found them, Jacob was holding my friend in his arms, protecting her with his whole life, Unfortunately Jacob didn't made it when they brought him to the hospital. When I got this news, I was devastated on what happened. Unfortunately, Mae wasn't able to make it to Jacob's funeral because she was in coma for two months. The worst part is, the one who organized Jacob's funeral is his friend Mark and Mark's parents because Jacob cut ties with his parents and he didn't told us about his family that much, maybe Mae knew about them since she's Jacob GF however she's in coma for weeks. Mae woke up in coma last month, I was so happy and sad because I have to be the one who needs to tell her that Jacob, her boyfriend died because Mark and I are the only one who knew that she and Jacob is in relationship cuz Mae kept it a secret from her strict parents but when I visited Mae in her hospital, She didn't remember me or anyone at all, Her doctor said, Post-traumatic amnesia typically occurs after a survivor wakes up from a coma so she had little to no memories at all, the doctor also stated that it will take a few days or weeks to regain her memories. I decided to not tell her about jacob yet because she just woke up with no memories and lost a lots of weight, So I don't want to just throw her a devastating news that her boyfriend died. A few days after Mae woke up, I visited her to the hospital but I was so shock when Mark is with her and acting like her boyfriend!? So basically Mark told her that he is Mae's boyfriend for a long time, I know Mark liked Mae since highschool but I can't believe he just betrayed Jacob who is his friend like that by pretending to be Mae's boyfriend, When we were finally alone while Mae does her therapy session with a nurse to practice walking, Mark begged me not to tell the truth to Mae because he wanted to experience her love and loving her as his own for once which was a total bs, but I was silenced when he confessed to me that he found out he has cancer for a while now, Mark wasn't able to tell all of us before due to the bus accident and Jacob's death and he had so much going on, so he just wanted to be with Mae for now, so that's why whenever I see Mark, he always looks like he didn't sleep and lost a little weight. It's already been three weeks and Mae has no sign of recovering her memory and she and Mark has been getting along and being happy in their "relationship " Should I tell Mae the truth? If you read it here, I'm actually just shitting you with the story I thought during a bus ride, lmao.