Send festive gifts, such as Tang suit wedding teddy bear dolls, crystal rose music boxes, and agate bead couple engraved bracelets for your niece's wedding. I think it's good. Giving them this bracelet means that you hope they can always be together and happy. It represents your thoughts and is unique. Consider it.
I don't know if you know that there is a crystal music box, which is very beautiful. You can engrave their photos in the crystal. If you search online, there should be many gift websites selling them. Send meaningful gifts, such as silver dishes and chopsticks, which are beautiful and fashionable, and are also good works of art.
Handmade chocolates are also good gifts, representing blessings to them. If you don't know how to DIY, you can ask the people in the store to help you. It's a very creative gift.
In fact, when your niece gets married, as an uncle, she will be very happy as long as you can send blessings. Every relative is like this. The expensiveness of the gift does not represent its thoughts on the newlyweds. On the contrary, only those who really care about it will move them.