This sounds positive OP, having some milk is good, even if it didn't all stay down. When DS had meningitis he was up and down for a good few days, so expect that. I got so wrapped up in the medical details - if his SATS were even slightly down, or his temperature was a tiny bit up, it would send me spiralling back in to panic mode. I pored over those charts and was obsessed with the machine he was hooked up to. Eventually (days in to the whole experience) a nurse explained to me that 'up and down' was a normal course for the illness to follow, and I started to calm down a little.
Someone else has said this but do try to eat if you can (and definitely get a huge bottle of water for your room). Adrenalin will keep you going for a few days, I managed a week on probably no more than an hour's unbroken sleep at any point, but lack of food made me feel really dreadful. Get someone to bring you in some really good handcream - after a few days my knuckles were bleeding from all of the washing and alcohol gel.
The one thing that I wish I'd done is to write down a little of what happened when my DS was ill. I know this sounds odd, but a year later I still think about it constantly, but my recollection of events is quite confused. I remember going to out of hours (2am ish?), being admitted to a paediatric ward, a consultant being paged in the middle of the night, a lumbar punture, it getting light, a second lumbar puncture, antibiotics, days in PICU, DS being a bit better, days back on the ward, various doctors, nurses etc. But in such a jumbled way. I wish that I'd written down even rough times of when things happened, when drugs were given, what the doctors and nurses names were. DH and I can't really agree on most of how it happened! It might have helped me to make sense of it all now. Maybe this is just how I operate, but I thought I'd mention it incase you felt it relevant to you too - sorry, I don't mean to harp on about my experience when you are right in the middle of this, so feel free to completely ignore me if it's not your style.
Sending all best wishes to you and your DD; keep posting, I will keep checking to see how you are doing.