I mean, a deal is a deal so from a logical perspective, OP is right. From a moral perspective, OP should be more considerate and understanding. A mother is quite possibly the hardest loss for people, and they said they'll pay them back.
Am I the a-hole Reddit story

AITA stories are always either "Someone hit my car, dog and house with a semi truck so I called the police, did I overreact?" Or " My daughter sneezed so I beat her senseless and she says I was too harsh", there's no in between

Somewhat. Even if something tragic happened like such, you should still be responsible for half of the payments made. If I were the roommate and my roommate didn't pay rent for a fair weeks, I would be upset too. Though it's also rude not to be understanding, and a recent passing, so it's a tough call.

I think the real factor here is how much time the roommate didn't pay for things like groceries, rent, and other payments. If it was very temporary, then yes. But if it had been many weeks or even a month without paying anything, then the frustration is understandable.

AITA stories are always either "Someone hit my car, dog and house with a semi truck so I called the police, did I overreact?" Or " My daughter sneezed so I beat her senseless and she says I was too harsh", there's no in between
Realll that’s why I love reading tthem lol 😭

OP did mention and clarify in a comment she made on the Reddit post that it was a one time thing and this type of thing had never happened before, where one of them couldn’t pay
I found a Reddit post and I wanted to share it with y’all.Before we start this is NOT my post. The OP is not me.
I (24f) live with a roommate (23f) in a small apartment. We split the cost for things like groceries, bills etc. About 2 days ago, my roommate’s mother passed away and she was very upset as they were very close. My roommate is busy with arranging the funeral, sorting out the will with her siblings, etc. She took a few days off of work so that she could have time for all of this and to have some time to herself. Because of this, she hasn’t received her usual pay check and is unable to pay her half for the bills, groceries etc. she says she’s really sorry and will pay me back when she goes back to work. She knows I make enough to cover it for this time and knows it won’t be an issue for me to pay it. But I think that she should pay it, as it’s her stuff too and not just mine, and I honestly think she’s just being lazy. I called her selfish and threatened to kick her out if she didn’t pay. My roommate called me an a- hole and said that I should have more consideration as her mother has just died.
AITA?
Lily’s thoughts:
Um yes u are. Do I rlly need to explain this? Imagine your mother passing away, and u take time off work to sort funeral arrangements, sort the will and to grieve. And saying that you are really sorry and will pay your roommate for the groceries when you go back to work. Your roommate is able to afford the groceries without your pay so money is not an issue, and this is a one time thing. And imagine ur roommate just screams and threatens to kick u out oml 😭
This is just my opinion, if u have a different one u can comment it 😊