AITA for missing my BILs funeral service

Back story: I'm (f61) am an solo pet sitter & dog walker. In 2020 no one could travel or working from home, so unemployed.
One kennel closed. Two of the local veterinary businesses stopped all boarding.

In 2021 things opened up for travel. My old clients started asking for service. Tons of new requests.
Typical day was up at 5/6 for 2 early pet stops 8/9 home, for my own dogs. Eat breakfast. 10 - 2 mid-days, break, 4 - 6 p.m. dinner breaks. 7- 9 break, 9-10 pm bedtime let outs.

Sept 2021. My wonderful BIL (56) had been dealing with a disease similar to MS. He died very suddenly. Dropped dead in the street within view of his own house. Very traumatic for my sister (F59 now).
There was a gathering at the house the next evening. I met my sister , told me everything, we cried and hugged for a long time. I was devastated for her.

Problem: I was told the services would be Tuesday at 11 am. The church is 40 minutes away from my service area. And I was massively overbooked. Several of the dogs I walk are reactive.
I contacted other pet sitters in the area to see if anyone could cover. They were overbooked too.

Told my sister all this, & that I would get there as soon as I could. I could tell her reaction was shocked that I was telling her I was not going to make the service. I had informed my elderly mother of the situation. I also told my adult sons who were going to be at the funeral.

I prepared all of my clients and let them know that I was doing quick let outs and short walks. I watched the service on zoom between let outs. Got there by 1:00. Gave my sister a hug, and talk to a couple of other people. I didn't think too much of it at the time. What I realize now was a chilly reception, I took for shock and grief.

So later that same day I get a call from my mother telling me that right after the church service my sister was yelling, livid that I wasn't there. My mother tried to explain to her again . She wasn't having it. She has not spoken to me since. With the exception of some brief communications about my mother's health.

My mother suggested therapy I was perfectly willing to go. She could yell at me all she wanted. She refused.
I made several attempts to call, message, none of my calls or messages were ever returned.

I gave up and decided to go to therapy myself (btw, better help is genius for us with long hours). It was great for understanding what she was going through. The therapist pointed out that my sister not only lost her husband under traumatic circumstances but that he was the main income. So she was facing financial difficulties. Also pointed out that part of the grieving process, anger, is sometimes misplaced. And that it was far easier to be angry with me, rather than at God, or my late brother-in-law.

I'm pissed It's hurting my mom, who's 87 and feels like she's in the middle. She has just us two daughters and five grandsons.