Hey whosthatgirl, welcome to the forums! I hope you're finding some helpful advice from our crack team of crack heads, as it were. Methamphetamine is a hell of a drug. My drug of choice was always Heroin and intermittently, Alcohol, but I've used Methamphetamine before. All of these drugs are addictive, but it's my firm belief that the pharmacokinetics of this stuff creates an amazing foundation for compulsive and chronic usage. You stay up one night, then you need a bit to pep you up cause you didn't sleep. Next thing you know, you've been up for 3 weeks and you're in county jail. I've only ever stayed up for 2 nights and considered that to be fucked in terms of its effect on my cognitive process.
I know that you're already somewhat familiar with this stuff, so you definitely have to use a bit of intuition to determine what you need in terms of recovery. Some people can act normal on this stuff and some people tweak the fuck out like that Wolf from Tex Avery. I would recommend continuing what you're doing. Hydrate, eat and try to sleep. You're going to have to use willpower and abort the trip. You should give yourself a full day at least to get that sleep debt covered. You have Benzodiazepines and these make this process a lot easier. Sedate yourself after eating, drinking and hygiene. Sleep for a full day or two if needed.
If you do all of this, you should be able to come out somewhat normal to your sister. You are right that it could be a huge trigger to come home to a sibling using their drug. That is my advice and I hope that helps.