Yes, it does hurt.
In those kinds of situations, we have learned to say "These people are highly-skilled and capable professionals who have practiced the right thing to do in this situation. They will do everything in our power to make this as easy as possible, and keep you as comfortable as possible. It will be over quickly (provided this is true) and you will be OK (provided this is a reasonable assessment.)
I've found actively lying in order to make him feel better makes it worse, and I'm betting there are many, many patients out there for whom this is true - even without autism to consider. You can find a way to sidestep the truth without breaking it, and it will increase your credibility with your patients.
I was in and out of hospitals a lot as a child. And one thing I remember clearly are the numerous times that someone said it doesn't hurt after I had said that it does. Even worse, I was treated like a bad kid for screaming and crying when it hurt. I remember when I had my first knee surgery at 10 and crying for hours because I was scared, uncomfortable and in pain. And what did the nurses do? They didn't even try to comfort me, they just put me in a room for myself "so I wouldn't disturb the other girls". You know what the effect is if children are constantly told their perceptions are wrong? The effect is that the child stops believing in his/her own perceptions arnd feelings. And it takes years of therapy to get in touch with your percpetions and feelings again. Trust me, I know first hand.
Heck, I've had multiple surgeries and experienced the same thing: nurses would come in, say I didnt need whatever it was, and I would insist on seeing a doctor, who would be horrified and immediately prescribe something appropriate. It's not just kids or autistics: our entire healthcare system seems to be based on "suck it up, kid."
People like that are the ones you tell you are autistic and they say,"well, we're all autistic, in one way or another." wow.
This:
My mom is like that. It has taken me a long time to "get this" because it really gets on my nerves. There are just people who like to live in a world where everything can be smoothed over by insisting it(whatever it is) is not so.
It doesn't make your wife a bad person, it is just that if this is a regular thing that she does, it will take both of you awhile to get each other on this. I would try to talk to her about it and try to make her understand that invalidating your daughter's feelings is about as counterproductive as you can get. (Be gentle, so she does not get defensive.)
Once you can get her to understand why what she was doing was suboptimal, maybe you can agree on a code word or something for you to say when she does that, so she can backtrack on her own and self-correct, so you don't have to correct her in front of your daughter. If this is her tendency it will be really hard for her to stop, and she won't even realize she does it, when she does it. It becomes automatic to people with this tendency. They really do not think about it.
I can really relate to this comment. Because no one was able to diagnose my autism until I was well into my adulthood, I was constantly told that my problems didn't exist, that I didn't have any challenges and if I accepted that then I would be fine. This has done a lot of damage to my psyche. Damage that I'm still struggling to repair.