That's really hard because not all parents can accept that. Some are in denial stage and would say no my child don't have a special need. Ask your cousin how does your niece interact with people, what she can do and not and from there you can tell about your observation with your niece. Tell as well your cousin that have an appointment with a developmental pediatrician but ahead of time you need to research for a developmental pediatrician in Batangas. Check for a nearest schedule because they are not the usual pediatrician that you can just go during their clinic schedule. You need to set an appointment first, I know that you can make it. Pray first that your cousin can accept your observation and for a guidance for you.
Magbasa pa