So, I actually missed the party. I didn't finish working till 21:00 but my friends still wanted me to come. She said she felt a bit akward being around her ex and his friends at the moment and wanted to wait for me, so we arranged to meet at 22:30. Just after this, I texted my friend to see if everyone had moved on (since they had started drinking at 19:00) and he replied that he was too drunk to stay out and had gone home. Her ex had invited everyone back to his flat and they were all there.
Her ex had been texting her all night trying to find out when she was coming and she had generally ignored him or made excuses. Since we had both gotten ready for a night out and I had come all the way back into town, I said we could just go out and have a few drinks ourselves or if she wanted to go to his flat and chill at the party I wouldn't mind - She wanted me to go with her to his flat, I said I would but I would rather go out. She texted him a few times explaining that she was with me and asked if I could come, to which he replied that he would be uncomfotable with me being there. So she told him we were going out for a drink and everyone was welcome to meet us out if they wanted to. He texted back a bit later saying he had changed his mind and didn't mind me coming as long as I would 'show him some respect'. I promised to her that I would, since I wouldn't disrespect someone in their own home and if he asked me to leave at any time I would politely leave. She said if that happened she would leave with me, but said she was having a better time out with me anyway, so she didn't want to go to his anymore.
We both got a bit drunk and bumped into some of her ex's friends while we were dancing and we had been kissing in the club as well. I don't think this group of people had gone to the house party at her ex's flat but I can't be sure. We were a bit worried, but they just said they knew what was going on and were happy for us. They were all pretty drunk too though.
She got so badly drunk though, that she couldn't walk and we got in a taxi back to mine. I spent most of the night nursing her, generally watching over her and getting her water if she wanted it. She was easily too drunk for us to have done anything sexual so of course, we didn't. She was really hung over in the morning, so apart from some gentle kisses there was nothing sexual in the morning either, which I didn't mind as I could tell she was feeling sick. She explained that she didn't remember much and that she wished that the first night we had slept next to each other could have gone differently. I nursed her in the morning as well, making her coffee and toast and just generally stayed and talked with her. I told her about her ex's friends seeing us, she didn't remember all the details so I filled her in and she was a bit worried at first but ultimately didn't seem bothered. I eventually drove her back to her Mum's when we had sobered up but she still looked pretty ill.
She text me a few times assuring me she was feeling better and I just said that I was glad. Probably won't see her now for a week or more (because of the distance).
But yeah, that's the party update. I'm still open to advice and I still want to play this carefully and hope for a relationship.