Braces - Not Happy with the Result

Braces and its effects are not permanent.
Meaning, teeth/the jaw, are always moving. And as a person ages, it shifts too. Still. It is not static.
Hence, a retainer should be worn, for life.
So that the placement of the teeth due to braces, stay somewhat in place.

I had braces for 3 years in middle school.
I still wear a retainer. At night. EVERY night.
Have to.
Otherwise, my teeth, shift.
My Dentist, even said so, and could tell what kind of orthodontic work I had done, and why.... Even though he had never seen me as a patient when I was a child.
So anyway, some adults, as an adult, get braces, again. Because, their teeth shifted.

And yes, sometimes if orthodontic work was not done correctly, or if the teeth shifts afterward, a person may get, jaw problems and alignment problems of their teeth and bite, still.

Get an orthodontist. I would never have settled for a look I was not happy with in the first place, orthodontia treatment is a contract if you're not happy you have them tweak until you are. Then you need a retainer (permanent or otherwise) to keep it that way. Teeth move.

They move your entire life. I know several people who had orthodontia work done and did not wear their retainers through college - now you would ask them why their parents never had their teeth fixed….. Make sure your new orthodontist is some one you feel you can talk to.

I haven't experienced this, but my orthodontist did tell me that I needed to wear my retainers nightly for the rest of my life. Does she have retainers? Is she wearing them? Perhaps an orthodontist could fit her for new retainers that would allow for a little movement and help out her jaw pain.

Do you mean overbite instead of underbite? I ask because I'm a little confused how in an underbite the teeth could hit the soft palate...
Regardless, I had an overbite and a gap also. I had the whole nine yards- head gear with brackets on the back teeth for 2 1/2 years, then a full set of braces for 15 mos. I have also struggled with jaw pain off and on due to the realignment also. However, I was also grinding my teeth at night which caused a lot of my problem. That and my gum chewing habit back then. :/
Is she wearing an kind of retainer? Permanent or otherwise? It's was amazing to me how fast my teeth moved once my braces came off. My gap started to come back in a matter of days. So, unless there something to keep the teeth in place, they will begin to move anyway.
If you are unhappy with the result, see your dentist. You might be able to talk to them about Invisilign. I know my dentist can do it this in his office without an orthodontist.
Hope this helps.