Are you sure she had sv? Its weird that she had d* for a day and then the v* followed for a couple of days after. Normally SV's last 24-48 hours...maybe it was food poisoning? In which case it would be impossible to catch!
I understand completely though. You're probably panicking about something that doesn't need to be panicked about You may have eaten too much fruit, or just eaten something a little off colour which has given you the d* but wont give you the v*...but because your flat mate had this, you immediately think its what she had. Im sure by now even if it WAS a virus (which i dont personally think it was) it wouldnt still be in your living environment.

Sip some water slowly to replace the fluidds you lost as being dehydrated can make you feel worse and very n*. Try to stay calm, google some breathing exercises and once you feel a little better (which im sure you will) get into bed and watchyour favourite childhood film or something that makes you feel comforted always helps me! Good luck sweet xx