Worried about dress after alterations

The initial stages of the alterations would tend to only get the basic shape closer. It happens pretty often that the initial steps don't look right. that is why you usually return for some follow up alterations. If you seamstress is qualified, it will turn out well. As to the neckline, no one will notice that it is a little higher now.

Tell your seamstress you want to keep the neckline where it is and you don't want to pull up the straps and cram your underarms. It almost looks like there's too much skirt? Maybe she can fix or add pleats as well. You should be getting 3 alteration appointments minimum to get the fit right. Don't be deterred, just speak up and see if she can fix it. If not, it may be best to get someone else.

You definitely have time to modify to your tastes or to find a new seamstress. Best wishes.