I had a similar problem with DD3 having a short bit a couple of years ago. She has really fine hair too, so clips never ever stay. The best bet was either one or two tight French plaits (ie one plait or pigtails) until it grew enough to reach the ponytail elastic. Normal plaits don't really hold with her hair, so it had to be French ones. Time consuming and faffy, but the only thing that works.
I agree on principle that you should take her back, but then again if it's too short, there's nothing that will make it longer!
sorry but layers are not supposed to be the same length they will be different lengths and it will make the hair more difficult to tie up and not as neat as a one length hair cut.
I would possibly go back and see if you can get something sorted but tbh a fringe cut in would work to get rid of the layers which are to short to go into the pony tail but then you will be stuck with a fringe and regular trips to get it trimmed (and hairdressers vary in their cutting ability of different fringes)
Could you use an alice band until the hair grows a bit? Hair grows quicker in summer so it shouldn't take long to gow longer again.
I had to take my ds back once, he was about 4 at the time with lovely long straight hair. They cut his hair with an inch difference on one side! They happily remedied it with an apology. I had to build myself up to go in though, (I hate confrontation!)
Take her back & ask them to re-do it without straightening it first
I took my 8 year old DD for a haircut about 10 days ago. She has quite long (halfway down her back) thick hair. I asked the hairdresser for a few layers through the front but the shortest layers must still be long enough to tie her hair up. The haircut took about 10 minutes, she did the layers very quickly.
When I went to tie her hair up on the next school day, the layer at the front on one side is much shorter than any other layer and just hangs there and won't go in her ponytail. I have to clip it up, but as it doesn't go in the hair elastic by the end of a schoolday it's all come unclipped and she looks really messy. Her hair looks messier down now that's been cut too. Layers everywhere and different lengths. It looked fine when we left the shop oddly enough, although the hairdresser did straighten it to cut it.
I feel so annoyed; I took DD for a haircut to make her hair look neater but she just looks scruffy all the time now. DH says I should go back to the salon, say that I stated that it had to be long enough to tie up and insist they figure out some ways that it can be tied up neatly. I can't do that though can I?