Rabbit and red back spiders

Does anyone have knowledge of pet rabbits?
Strange question to ask here but I would love to hear from people with experience if there is any.
I had a Dewarf Lop rabbit, she was 10 months old- I got her at 7.5 weeks.
She was loved so much in our house, she lived a life of a queen.
Well cared for, well fed, vaccinated, wormed ect..
Anyway, today I noticed she wasn't her normal self, I couldn't see anything to un normal other than she was quiet, I sat with her giving her cuddles for a quiet a long time, put her down and went inside. When I came back out she had passed away.
I took her bedding out of her pen and I found a red back spider in there.
Now I'm thinking she may have been bitten, but does anyone know if they are deadly to rabbits?
I have tried google and can't find a direct answer.
I am absolutely deverstated.