I have had covid symptoms since Thursday night and my sister who lives with me is negative with no symptoms? How likely is it that she won't have it?

I've tested positive for covid. She tested negative and has no symptoms. Is it possible to not catch it even though you live with someone?

Its day 4 of my symptoms. Should I think she is the lucky one and she would have got it by now. I am worried about her as she has underlying health issues
I have had covid symptoms since Thursday night and my sister who lives with me is negative with no symptoms? How likely is it that she won't have it?
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