Subletting deposit problem

I have a bit of an issue with a place I recently moved out of.

I found it through spare room and it was available straight away, which was perfect as I had been offered a job last minute and needed somewhere to live. It was advertised as being someone needed to 'share the rent', and with bills included.

There was no written contract (stupid I know), but it was verbally agreed that I would pay a months rent in advance with a deposit of 600, to include all bills (unless any large bills came through) and the other tenant said she was happy for guests to stay whenever, no need to warn her. She stated it was a casual agreement and that just to let her know a couple of weeks before if I wanted to move out. She let me move in two days early, and refused my offer of rent for this period. I moved in over two days, sleeping at my old house once I had moved half my stuff. On the second day, when I planned to move in completely, she asked me to come late in the day and when I got there it was evident that someone had slept in the room (which she admitted to). I was a bit surprised but let it go as I wanted to get on.

As I stayed there it became evident that it wouldn't work for me- I am a shift worker, and she would get home at all times of the day and night, with an assortment of different people, and would make a lot of noise. She had people staying on the sofa every night, and I felt quite unsafe because I never knew who would be there and didnt have a lock on my room. I also had suspicions of drug use going on +/- other dodgy activity due to the smell of cannabis from time to time and odd noises coming from her bedroom, where she seemed to entertain a varying number of guests. It became evident that her parents own the house (she was a bit shady about this though), and they came with no notice one day to fit a curtain rail in my room, which again concerned me.

My partner then got a job in the same town so we made a decision to move in together. I gave her two weeks notice, which she seemed fine with, as she hadn't taken down the advert and had people who could move in on September 1st, and I moved out as soon as the new place was sorted (I didn't see her to tell her the exact date in advance as I was going to my parents at weekends to get some uninterrupted sleep). However, this was a week before the end of the month, and as I had paid rent and wasn't expecting it back I didn't think this would be an issue.

I went back the day after moving my stuff to collect my bike, which only fits in my partners car. She asked for the keys back, stating that she had let the room out on couch surfing for the next week. I asked for my deposit back prior to giving the keys back, and for a quarter of the months rent as she had managed to let the room already. She immediately became very angry, and stated that as I had moved out early it was up to her what she did with the room in her house, and that I wouldn't get the rent back. I hate confrontation, so gave her the keys and said I would text her the bank details for the deposit. My partner said to her that this seemed unfair and that she shouldn't be letting a room that I have already paid for without returning my rent. She then turned round and said she didnt know him (despite having met the couple of times he had stayed) and that she would call the police if he didn't leave. He obviously left fairly swiftly as did I. She then shouted at us across the road as we put the bike in the car, accusing my partner of 'anger issues'.

I sent a text to her apologising for upsetting her, as it all seemed a bit odd and I didn't want to risk not getting my deposit. She replied today saying that despite me and my partner being 'accusatory and aggressive' (which we really weren't) I would get my deposit back in September when she has relet the room, minus a contribution for gas and water 'as agreed' because my partner had stayed a couple of times.

I am a bit shaken but want to know what my rights are as I strongly suspect she won't pay the deposit back. I have proof of paying the deposit, and the spare room advert stating bills are included. I am unclear whether I count as a Tennant or a lodger. Should the deposit have been in a deposit protection scheme? Is there any way I can claim back my rent for that period?

All advice gratefully received.