I'm sorry it hurt so much, but you lasted and the end product is beautiful! The story behind it is tragic and I hope only the best for you and her. Let's hope it's at an early stage and that she will pull through fine! As far as your tat goes, it looks like it was well worth the pain. Your sister's tats look great as well! Did she have the same types of problems with pain that you had? Generally, if the needle is bouncing against bone it tends to hurt a little bit more.
As far as my tat experience goes, I have three. I got the first done in Prague when I was fifteen without parental consent...so I was one of the few kids in my school that had one, but it's on my hip in the front. I went in expecting pain, but the worst was when the needle was actually hitting my pelvis xD. It's just a nautical star, the kind that almost everyone has. My next tattoo I got when I turned 18. I saved up specifically for it, knowing it was going to be expensive. It's a side piece that stretches from damn close to my arm pit down past where my belt usually rests. It's of a naked anorexic woman with her head cut off; flowers are growing out of her neck based on this painting:
https://elleir.deviantart.com/art/Abysse-93065796
It's more of a long tat than a big one, but it still took five hours on the table, all one sitting. $500 later and I'm left with a product I very much do not regret. But then, the painting means the world to me. My final tat (though hopefully it's only temporarily final; I want many more) is of a tribal type tattoo of a spider. I've long wanted a tattoo on my body of my favorite little creatures but I couldn't decide on a species, so it was off hunting for vague looking art and I got it. It's on my arm, and was done in my friend's bedroom by said friend. He's an artist and was just starting tattooing so I was nervous but he did a really nice job and delivered exactly what I wanted! This one was my least painful by far, probably because of the lack of bone there. This is the only one that most people see.
If you're wanting more, maybe try some of the stuff that Mekatra suggested? I actually kind of like the pain, looking at it as sort of making the experience authentic, but I totally understand, especially if your future tattoos are going to be on more sensitive parts of the body. Your tat was pretty large and involved a lot of filling in, so I'm wondering if maybe that's where some of the pain came in? From my experience though, the fine lines hurt the most, haha. Sometimes it helps if you have a hand to hold, or something squeazy! For the most painful one (my side one) I had a little spider key chain that was one of those that you could squeeze if you got stressed....sadly, it didn't survive the encounter,lol.