I understand special needs, but won't giving into all the quirks of OCD just make the rituals even worse? Shouldn't the parent instead work to confront these rituals in many small ways daily, regardless of meltdown, in order to help the child overcome the obsessions and eventually learn to compromise within normal social settings?.
It's not that simple. First of all OCD isn't about a child not knowing how to compromise, the OCD kids I know can often compromise fine, as long as the issue isn't a compulsion or an obsession. I'm going to tell you a story to give you a sense of why sometimes a mother might make the choice to let something like this happen.
I had a little boy with OCD in my class one year. Some of his compulsions were dangerous. For example, if an object, or a part of a person, hit into something he had a compulsive need to touch that place to make sure it was "OK". Sounds OK -- well if a ball from the playground bumped a parked car on the other side of the street he'd run to touch the car, unaware of the other cars moving in the street. If another child was kicking the underside of his desk, he's crawl under to put his hand between the child's foot and the desk to try and touch it between kicks, he was fast because he "needed" to touch the spot before the foot got there again, and if the other kid didn't notice (or didn't care) and he got kicked -- that was not a deterrent.
He also had a compulsion about licking things, specifically things that other people had touched, like light switches, and door knobs and toilet seats -- I don't think I need to go into details about that.
He also had an obsessive need to have a pencil with a "good eraser", because it somehow magically warded off mistakes before they happened.
Did he have these obsessions because people "gave in" or "indulged" them? No, he had them because he had them - I'm sure there's some deep seated psychological theory, but all I know is that neither we, nor his parents, ever let him run across the street, nor did we let him lick the toilet seat -- not once, and yet he continued to try.
For him, at least, and I can't speak to other kids with the same disability but I wouldn't be surprised if this was true, he had a sliver of ability to control the compulsions and obsessions. For example, he helped us make a vibrant red "stop sign" to hang on the toilet, and if he saw it and if he could sometimes remember to lick a shiny bracelet he wore instead, and if he knew he wasn't going to have that much self control, he could usually remember to ask someone to come with him and physically stop him. We had another child in the classroom, who would sometimes throw tantrums and kick the trash can as hard as he could (big improvement, when he arrived he'd kick staff members), and sometimes, the little boy could be satisfied to touch the other side of the trash can, whereas other times it was all he could do to tell us that he was going over there to touch the trash can (that is to put his little hand between the trash can and the foot of another child who was kicking it as hard as he could) and we'd have to chase him down.
But doing these things, controlling the compulsions was exhausting, and just like a child with a physical disability might be able to walk around WDW in the morning, and yet 100% need a wheelchair in the afternoon, he could easily run out of steam. It was a constant balancing act, because like exercise, some practice controlling the compulsions was good because it built stamina, but too much lead to fatigue and actually made it harder to do the same thing tomorrow. We had a chair in our classroom (this was a special ed class if you haven't figured that out yet), with a seat belt for a child with a physical disability. The little boy could do up the seat belt, but couldn't undo it (it wasn't designed that way, not intended as a restraint, just intended to hold a child's hips back so they didn't slide around, but the clip was tight and his fingers were small). Sometimes, near the end of the day he'd be so exhausted from trying to stop himself that he'd climb in and buckle himself in the chair because he just couldn't face the work of trying any longer, and he also couldn't stand to know he was disappointing us when he failed.
Anyway, like I said, this little boy had an obsession with pencil erasers. In my classroom I had a rule -- when it comes to pencils you "get what you get and you don't get upset". You don't spend writer's workshop whining about how your pencil's too short or the eraser's almost gone -- you spend it writing. I've had that rule for years, and I made every single kid in my class follow it. . . except him. He got a pencil with a beautiful newish eraser every day. Because I knew that if I didn't he'd get over it, but that priceless bit of energy or will power he needed to get over the eraser would then be used up, and chances were that later in the day there's be a ball that went into the street, or a trash can to touch on the side, or a toilet to not lick, and he'd need that precious bit of energy, because maybe today would be the one day I wasn't fast enough.
In addition, I knew he was working hard -- all day long he was working to stay in control, in fact he was probably working 10 times as hard as I was, and he was only a very little boy. So by giving him the pencil with the nice eraser I was able to say -- "I know you're carrying a big burden, and you do it so bravely, let me take this tiny piece from you".
Was that going on with Sarah? I don't know. Probably not. Maybe she was a spoiled snowflake. Maybe that wasn't her mother and her mother died the week before (grieving kids are notoriously controlling), or maybe she was recently diagnosed with some condition that impacted her food choices (like celiac) and mom had said no a thousand times during that trip to the store and decided that, just this once, she was going to say yes. Or maybe she was a spoiled snowflake.
Unless Sarah's parents come here and tell us, we'll never know.
I agree, I have a very strong willed child, he is 20 and still afraid of me, as he should be 
