Resident fall

I need help. I feel terrible. I don't know what caused her fall, but she fell. This is my second week out on the floor and I'm still shadowing but I'm as allowed to have. 4 people on my own lineup. I was trained with this person and assisted in transferring from wheel chair to toilet and back and etc. but I was being watched but never needed any help. Well, this time ie as alone, and my resident (has weakness in one side of her body) but she was a one person assist, but extensive. But she had asked to get up off the toilet so I told her okay like I'm going to get your wheel chair adjusted to you closer and lock the wheels, and I talked her through it after  explained every step. Anyway we got her to stand and she holds onto the bar but then suddenly as I was sitting her back (she wasn't leaving back like with her butt to sit in the chair far enough to fall backwards) she had like pivoted with her leg the opposite direction (late I found out she was more weak in that certain side of her body) which then.made sense on how she fell. Well I had to hurry and move the wheel chair so I unlocked it to push it out of the way. And her family was actually in the room next to the bathroom. Anyway that was yesterday. Well today the family freaked out on me even after I've already felt super guilty... and told me not to try to defend myself that they know what I did and didn't do. And told the resident their mom that I didn't lock the breaks Bc when they came in the wheelchairs breaks weren't locked, but I unliked to move it out of the way fully. And I jus, the family was being super rude to me, and I complied with all of their questions and remained super respectful as they jus say there and talked rudely and horribly toward me. And I feel like super super upset Because when he nurse evaluated her (that certain side of her body) wasn't even working at all she couldn't even move it really (sometimes I guess she will go through gases like that) and I jus feel super horrible. And I really love residents and it's my first in this field and I'm only 20.