If she wants a priest to officiate, the actual ceremony will most likely not be permitted to take place at the hotel. It can, however, be celebrated in a church or chapel. At least, that is the way it is done in Puerto Plata.
Since Monse?or Pe?a, the current bishop of La Altagracia Province (where Punta Cana is located) is the previous bishop of Puerto Plata, I am fairly certain that this is correct. You can PM me if you want a telephone number for Bishop Pe?a (who speaks English) to discuss this with him.
I can tell you, however, that if she wants a Catholic ceremony, she will have to comply with all regulations, including a marriage preparation course (Pre-Cana). There is a list of required paperwork (things like baptismal certificates and permission from her pastor) that must be completed. I believe that I have a copy of the requirements for Puerto Plata which would be a rough guideline for what she'll need in Punta Cana. Contact me if you wish.