In addition to what battie said, a simple 'I can't really do much for you as 1) this is a virtual conversation 2) I'm several years away from being a doctor, and I'm in my first semester of school.'
Alternatively, if they aren't 'important' family/friends, just ignore them. I've got quite a few unread FB messages from distant friends/family asking me for vet advice/please come look at my pet at 3am/etc and I feel absolutely no guilt just ignoring those. And sometimes going as far as deleting the person off my social media entirely. I've since deleted FB messenger from my phone entirely because it was getting so bad, I was getting messages from people I don't even know because someone shared my name and told them to contact me. If they keep reaching out/suggest it is an emergency, absolutely make them feel stupid (in a roundabout way) for handling an emergency situation via text/FB message/insta DM instead of seeking emergency care.
If someone is going to treat you like **** for being unable to help, I strongly encourage you to throw that back at them when they come around again (because they will). 'Sorry, can't help, I'm useless remember!' and then leave it at that. Include screenshots if indicated. But then again I have no issue being petty and passive aggressive when people treat me badly. You're not a free resource to people and have no obligation to be one.