A super soft stuffed animal that is verified child safe as in it does not come apart easily and/or have small parts one could choke on. It should be something really cute that both the Niece and other family members will be happy with. Send links and pictures of your ideas to the other family members for their input.
It's been a while for me. Try to find a local specialty shop with a very good reputation that carries children's toys and collectables. Local because you can feel and inspect the toy and you are dealing with someone face-to-face. If you have a facebook group for your local community they will have ideas. Yelp may also have some suggestions despite being heavily gamed. Read the negative reviews. Local shops will cost more than online but it may be worth it in my opinion.
If there is a Children's Hospital near you they usually have unique things in their gift shop also pricey but worth it.