People on the spectrum generally lean towards practical expressions of affection and interest rather than emotional ones, but even if I thought that maybe someone was 'just being nice', I'd tend to wonder why they were being nice. Personally, I don't often find people are that nice without a reason, so it would still tend to come back to concluding that you were doing nice things for me because you liked me.
That doesn't mean I'd know why you liked me!
I didn't think I was on the spectrum - I had the same idea of autism as everyone else, that it was for kids and you could tell by the rocking and hand flapping, and being non verbal, etc. I didn't recognize myself as those things, even though I ticked many of the actual autistic boxes, such as being 'shy' and insular, not making eye contact, being susceptible to high stresses, needing to do things to decompress - walking, typically, needing quiet/dark/dim spaces and the like.
My employer suggested I might see one of our expert witness psychologists who could possibly help understand why occasionally I seemed to have difficulties interacting with colleagues. It was he who diagnosed me after a long pair of sessions answering questions and taking tests. I was totally shocked.
Then it made sense. I had bought a few books and read them, and I realized my youngest daughter was being described in them - she is on the spectrum too. Once I realized she was autistic, it was easier to see how my characteristics fit, particularly when discussing it with her.
Your daughter's sensory experiences sound very typical. Stimming can be something NT people do too, because it's a human reaction to stress and pressure, which is not isolated to just neurodivergent people, but if she seems to suffer prolonged anxiety too, that would tend to suggest she's on the spectrum.
A lot of children have problems at times with showers/baths and things like brushing teeth, but when a child has issues with water because it feels bad on the skin (this happened to me for years) then it does tend to be a sign. It's often the texture of things, so you might find she likes some clothing more than others, and you might find if you look at her favorites, they're all the same kind of material. Or for me, clothing tags - they drive me up the wall because they're like my skin being burned.
Meltdowns are the crucial behavior though. While NTs have meltdowns too, they tend to be as a result of different things - anger for example - while on the spectrum they tend to come from prolonged overload with no opportunity to escape. NT kids may therefore meltdown during arguments and confrontations, where ND kids will tend to from bright lights, ongoing sound, lots of activity around them. If an ND kid can't escape the constant 'input' and can't stim the stress away, a meltdown will be very common.
When she has a meltdown, if she's NT, you can typically help bring the intensity of it down by controlling her, but if she's ND, you probably can't - and if you try the meltdown may even escalate. Try sitting with her, giving her fairly firm physical contact such as your hand on her knee so she can feel you present, and then just tell her you're there when she needs you. Nothing else than that. That reassuring presence, but no direct intervention, usually gives an autistic person chance to get the situation under control themselves - though at 10 years old she's probably very confused and even frightened by a meltdown when it happens. If she flails her arms, don't try to stop her, just make sure she doesn't hurt herself by clearing things out of the way.
