The details you outlined are created by the fabric patterns of original dress, instead of adding extra sequin fabric. Thus, the whole details on the dress are harmonious and comfortable.

Your dress was made from our bombshell sequin fabric as agreed, so the details you outlined above can not be created by that bombshell sequin fabric.
We have to cut sequin bands from sequin fabric and hand sew them to the neckline and sleeve cuffs, which might not work well with the whole dress. Additionally, it will make the neckline and cuffs thicker. Extra 50 USD for this alteration.
Please kindly note that if we make the change now, the production time will be delayed. Especially at this peak season.
In my opinion, it is better to decide whether to add this change after checking the finished dress. And your time is a good friend since your prom is in May.
Please kindly let me know your thoughts.