Have to say, the IQ is about what you would expect from the Tamron.
Focus was about spot on. That is, the focus plane is pretty much right.
You want focus on your daughters face, but remember that focus works on a plane, it's not really a spot as such.(more accurately DoF works along a plane.. but same difference)

Very important to note here(I downloaded and checked the image in VNX2 too) .. your upload of the cropped image is magnified more than 100% .. so it's exaggerated the softness of the lens.
I believe you may have set magnify to 200% and then cropped.
At 100%(in VNX2) .. don't look too bad.

So the focus spot on your daughters lower skirt, is close enough to the same plane as is her face .. and therefore her eyes.

Of note is that these consumer super zooms will render images as you experience. They're never going to be as good as a higher grade of zoom lens.
The Sony camera you mention at $3K .. is camera body only!
You haven't taken into account that a lens is still required.

summary: if you take a $3K Sony camera(that is supposedly that much better than an old 'decrepit' unworthy D90) .. and add to this $3K camera the same Tamron lens you used, you WILL get close to the exact same IQ.

It all starts at the front, and ends up way down the back there, through the camera sensor and onto your memory card. The important point being the start.
Feed in better quality, and you'll get better quality all the way through to the end!

So as you shoot more, and gain more experience, you see more/different ways to do stuff you want to achieve.
Note how you set the Tamron at 46mm focal length.
Assuming you're at the sidelines, so can't step in a little(just one step) .. you could have used the Nikon 35, set it to f/2.8(very sharp there, or f/4: supposedly a little bit sharper again), ISO would have adjusted to ISO100, shutter at 1/2000s for those conditions.
But if you wanted to keep the same framing, because the Nikon 35mm would have given a sharper image, you could have had greater ability to crop more.

etc. etc.

ie. there are "many ways to skin a cat" .. it's a matter of building up the experience, or simply asking how to ....

I have to be honest, I'd be happy to have captured that image of your daughter. It may not be the greatest detailed image you have, and maybe in the future you do get a better camera/lens, and you get better quality images, but at least you have what you have and in reasonable quality.
The important point I hope to help with is that you don't usually print/view images at 100% pixel view(that is zoomed in all the way).
Learn to appreciate images for what they are, not the fact that you got that last 0.01% out of the gear that captured them!

That's basically what I do:
I use cheap @$$ed gear, trying more so to do more with that, then to spend big $ trying to get that last percent of quality.
Revelation here tho!! I do spend big $s on gear sometimes, but not 'willy nilly'. eg. I did buy a D800E way back when and that cost me over $3K too, but I didn't buy it because it gave me better IQ.
I bought it because I wanted something specific from the next camera.
back then video in cameras wasn't common, and the two specifics I wanted were video and full frame capture(due to most of the lenses I have). D700(much cheaper) didn't have video, and D3s silly price for what I wanted. Would have loved a D3s, but you need to balance common sense with reality.

Later .. much later, I then got a cheapo ultra wide angle lens, as my primary choice of subject matter was(still is) landcapes.
I used my APS-C only Sigma 10-20 lens for about a year till I finally decided on which wide angle lens to finally get.
Nikon 14-24 was a great lens, awesome lens, much better IQ than the Sigma 12-24 of the time, the cheaper model f/4.5-5.6 version. Later Sigma created their 12-24 f/4 lens too. but wasn't an option(around) for me when I finally got mine.
Again, the Nikon 14-24 was big bucks, even tho I did a lot of photography back then .. still decided that in landscapes absolute detail wasn't as important as the overall image .. ie. the subject was more important than the detail captured of that subject.

So if I ever displayed the images, the additional cost of the Nikon 14-24 over the 1/3 priced Sigma 12-24(old model) just wasn't 'money well spent'.
I got better tripod, and more other stuff(left me some money to aim for another semi expensive lens too).

So sometimes you need to weigh up what are you doing and why.
ie. what are you spending, and what do you want from it?
Sometimes a better lens is the best way to go, other times a better camera is the way to go .. and so on and so forth.

If you want a half decent cheap zoom lens to get high quality images at the short range, I can highly recommend the Tamron 17-50/2.8 lens from ways back.
There are multiple versions of this lens, second hand they're quite cheap, and IQ is much better than the price would indicate. I estimate between $100-300 for a good one.
The non VC lens will be cheaper(this is what I have), and the VC lens will be at the higher end. Brand new I think about $500-ish. VC is handy to have for longer shutter times.
The other nice Tammy lens I can't part with is the 28-75/2.8. One thing that stops me from recommending this lens is that mine backfocuses. Now that I got used to it tho, I work around that if I use it.
But it's sharp enough at f/2.8, gets sharper at f/4, and why I like it is that it's bokeh is about as good as you see from any lens out there.


The beauty of owning a D90 Nikon camera(and not a more modern D5xxx) is that your model focuses with AF-D lenses(has a built in af drive) .. so you have more options for AF lenses.

if you wanted more zoom range lens, I like the 18-105 and 18-140(have both) that Nikon make. Good IQ(not the greatest) and decent zoom range.

If you really want spectacular image quality worthy of a $3000 spend .. you need to look at some pretty decent lenses.

last tip: if you're still using ViewNX2, open the NEF there, and just give the image a 2 setting on sharpening.
If you're using ViewNX-D, make the sharpening settings a little different. A bit convoluted so will explain this only if you wanted it.