Sitting on the edge of bed

We recently moved to a new house and have my mum staying over to help. She is sleeping in my daughter's room on the floor (double bed) and our daughter sleeps between my husband and I in our super king bed (not floor bed). She's okay between us but last night I went to pee (not even 1 min!!!) and I came back to her awake, sat by the edge of the bed. She did not fall but now she knows hot to roll from back to front and sit, she does it all the time and I am terrified she'll do it again and fall... She is never in the bed without us, but I can't help but think 1 second of being inattentive is all it takes... Would bed rails be a solution as she would never sleep next to them but could catch her when she sits next to the edge ? Would rolled up towels or pool noodles be more appropriate for her age to prevent her from sitting when she's on the edge? I've been trying to teach her to get down the bed safely but she's only 10 months... We cannot put the super king mattress on the floor as we do not have enough space. On the bright side, since she's been sleeping with both of us and not just me, she's been sleeping long stretches (up to 8h30) and seems to fall asleep more easily. Once again, she's never unattended on the adult bed, I should have woke her dad up when I went to pee but I thought she was sleeping too...