PLEASE HELP!!my cat wont stop hissing at me

my fiance and i have had our cat for four years, she is an absoluutely gorgeous, affectionate and loving black short-hair. my fiance has been away for a few days (although this is not out of the ordinary) and the Matilda (cat) and I have gone along as normal.
until yesterday when late last night i went out for 20 minutes (didnt pet any strange or obscure animals) and when i returned she hissed at me and attacked me when i approached her!! she did this continuously for about 18 hours and has since got a bit better.
Help!!

Did she hurt herself while you were out? I know you can't check her as she won't let you right now - but was anything out of place when you got back? (did something fall on her?)

I'd just give her some time and ignore her for now, if she's not actively attacking you. Just don't try to approach her - and literally ignore her.

It's possible she saw another cat outdoors, and you're the recipient of redirected aggression. And it's possible you rubbed up against someplace a male cat had sprayed. You just never can tell.

Does she act normal if you don't approach her?? Does she sleep, eat, drink and play? Because if she is constantly alert like this she might be in some kind of pain.