Any help for me for my sleep walking child ?

I don't really know what to do ! I remove the door keys at night so she can't escape but several times now she's wondered off downstairs whilst I'm asleep and I don't hear her ! she's been down last night and it looks like she tried to make coffee ! she came down whilst I was awake too she walked downstairs and sat at the bottom had a wee and went back to bed , she peed all over herself and the floor I didn't realise at first untill I went to check on her and stood in a puddle of pee ! she also wonders to the downstairs toilet pees on the floor and then gos back to bed ! but there's a toilet upstairs so I don't understand why she's coming down and peeing on the floor it's right next to her room , I ask her about it and she has no memory of doing it or me taking her clothes off and cleaning her up afterwards last night ! I've no experience with sleep walking so I really don't know what to do ? I don't want her to hurt herself in the process whilst I'm asleep ?