My very young sister cut herself a ton last night

My younger sister, who is 10 (turning 11) so VERY young. I know this can happen to any age group pretty much, I’ve done it in the past but I was 14-15 I think. She is constantly online, my mom won’t do anything about it, won’t ground her, nothing. She has a phone, tablet, computer, and vr headset (this is the big one)

She doesn’t get out of bed, this isn’t specifically from any depression, instead because she’s on her headset 24/7 playing vrchat with god knows who.

She (let’s call her Y) is constantly having her friends (no idea how old) say they’re going to kill themselves. Some tell her days, some just do it. But she’s had at least eight people kill rhemselves, threaten to do it, or set a date and tell Y about it.

I don’t know if this is true cause it’s word of mouth obviously, but either way. If it is true it’s obviously putting way too much stress on her. The cuts were all over her right forearm and it’s a lot at once too. They’re shallow albeit, but knowing her she won’t clean them.

She denied it immediately and while my mom didn’t believe her at all, my mom still didn’t do anything about it. I need help convincing my mom to get Y help because I’ve been there and nobody helped me, I’m not having that repeat. I’m already stressed enough and have been thinking of relapse after being clean for 3-4 years. I haven’t and I have friends to help me now, but I need to get Y help.

Sorry for the ramble, this just happened and I don’t know what to do