Your niece and you must have a unique bond for her to share her dream. In a dream of a mother elephant seen with two baby elephants is also a rare picture.
A mother elephant can have in a span of 50 years a baby about every 5. A mother cow will stay with baby for about 5 years. In a herd of elephants, the leader is a pack is a female elephant. She is the boss. There are no males. The bulls stand alone or join a male group.
The elephants have big of everything. So, your niece must have something big to handle. But, two things are comforting her. They are equally important and she will have to gently consider how to manage it all.
Other: Is she expecting? Did she recently become a single mom? Does she watch other children beside her own? Foster care. Considering adding and having a another baby into her family. For a mother elephant to carry twins is extremely rare. It can happen. If it does happen and one is lost, then, the mother will perhaps mourn. After 22 months of pregnancy, why wouldn't she not? Elephants are known to mourn. They can return to a spot of a lost loved one.
In the herd of elephants, each elephant stay tight to protect and help each other. They baby-sit all the calves.
They line up single file. Mother, sisters, daughters and they carry on and march on!
This is just one angle of the dream breaking.
And, it can be the wrong angle. Just thoughts.
https://www.womenshealthmag.com/life/a19983985/elephants-make-the-best-moms
https://www.independent.co.uk/voices/comment/six-facts-about-elephant-families-9015298.html