This seems pretty bad as well, not acknowledging the impact being stoned can have on perception of time / what went on in the evening, nor the impact of 3 days solid of intensive questioning with hardly any sleep in terms of implanting false memories in someone's head, and making their memory and judgement all go pretty trippy - especially someone who's been traumatised by find the body of their flatmate.
I remember when a mate of mine committed suicide, I woke up a couple of days later with this absolutely vivid memory of having seen him jump, then staggering around taking a few minutes to die at the bottom. Talking to a mate about this later he said that he'd spoken with people who actually did see it, and that was what had happened... but I definitely wasn't there, as I was running a club night across town that night with 300 people in it. To this day though I've got this scene of it happening stuck in my brain as if I was actually there watching it, when I definitely wasn't.
The mind can play some strange tricks on people, particularly when they've been taking drugs, and / or are very sleep deprived and in a stressful situation.
to me, had she actually been a killer trying to cover her tracks she would never have been saying any of this stuff, the fact she is saying it just makes her seem a lot more like a scared, confused, sleep deprived kid who's just undergone a pretty horrific ordeal in the police station.
The alternative scenario to explain her bizarre half memories of things being the impact of the weed they'd been smoking, and anything else they'd been drinking / taking. It does sound pretty like how I'd sound if attempting to explain my memories of events around the night I ended up in hospital having chucked something through my own front window and dived through after it while completely off it, after having been chased down a back alley and nicked by a copper, and a couple of other or a few other occasions. Not that this in itself would mean she was or wasn't the killer, just that it'd explain why her and Rafael seem to have struggled to piece together what they were doing that evening
If people are going to be analysing these letters etc that's definitely the element of them that seems to be the most worth considering the implications of, rather than the bullshit of trying to link her mentioning of water with sexual desires or some such twaddle.