i'm so sorry to post again needed more reassurance but here's the thing...

basically, my little sister went to london yesterday with my dad and his girlfriend's family, and she has a 5 year old daughter. turns out she had a tummy ache yesterday and v* in the evening (after my sister had left).

my fiancé and i had an engagement party today, and my little sister ended up staying last night to help me out. i didn't realise then that my dad's girlfriend's little girl had v*. i'm not sure if she v* once or more.

please help! am i correct in saying that as long as she didn't v* whilst my sister was around, my sister can't catch it? or because she had a stomach ache, she was contagious and my sister could have been carrying it?

and if my sister was carrying it, have i just let a deadly germ in to my home?! HELP!