Suit tailoring

No, the shoulder fit is very important and should be right from the start. I suggest you exchange it for your proper size.

No. The single most important area for a suit to fit you correctly is in your shoulders. If the shoulders are too big, you need to get the jacket recut. That tends to be an expensive operation. If you sense the shoulders are too big, they probably are. I'd exchange the suit for something that fits properly. Once you get the shoulders right, you can look at other alterations.

If she returns to the shop alone - get refund
If you go to the shop with her - try on different size jackets

But it is possible to tailor shoulders to be smaller, if you can not return / wish to keep.

Take it back and get the correct size.