Are you staying at the Poly? If so, there are a couple of options.
1) Add cousin to your reservation, if you are not already at the room occupancy limit (5 persons + 1 child under the age of 3). She will then be able to get a wristband allowing her access to the Poly pool.
2) If you are going to the pool with her, you can ask the lifeguard for permission for her to join you. The lifeguard has control of the pool area, and MAY allow this if the pool is not crowded. They may also say no. It's entirely the lifeguard's decision.
If you're not staying at the Poly, or if you can't add her to your reservation or weren't going to join her at the pool, the answer is no, she won't be able to use the pool. The Poly has become much stricter in enforcing the pool use policies.
This thread is closed; for further questions or discussion, please see our Pool Hopping FAQ at the top of this board.