Accommodation for my sister

My twin sister is 36 & has cerebral palsy and still living with my parents. My parents are 63 & 65 & are winding down from farming after doing most of their lives. When we were 14 our older brother was hit by a car & devastatingly to us all he died. I know everyone has difficult times but I feel my parents deserve to be able to go on holiday and not long before retirement they don't want the worry of where my sister is going to live. They don't want to be in a situation where if they did she will just get put anywhere. They have been trying to get help from ss but have been utterly useless with her case being passed from pillar to post & nobody fighting for her. We have found somewhere that she is happy with to live but in a different county to be near myself & younger brother so that my parents have a bit more freedom to travel & if anything were to happen to them. We have been trying to get ss to take a look at the place to try & get funding but refused to look. They suggested somewhere in local area so after going there & finding narrow corridors & doorframes  & no space to turn corner into bathroom or room under sink for wheelchair to wash up plus place was filthy & place not registered Care Quality Commision & staff didn't seem to care there was no way she could go there. Since that's been said we haven't heard anything -apart from the social worker has moved her case to another sw. They keep saying they will help but NEVER do. Everything is such a battle with them. I really feel time is running out with my parents age. They used to be very fit healthy people but my mum keeps having falls & my dad is weaker & has so many aches & pains & I don't want them to have this stress nor do I want my sister to feel like a burden. Any advice on how we can help my sister's situation would be massively appreciated.