Not my mom but a few years ago I gifted my grandma a cup. IDK if Nicki is popular outside of Germany but they are mainly cute animal plushi and have some other merch too like pencil cases, keychains, jewlery, etc. and mainly amed towards kids but that doesn't means adults can't enjoy them too and I had a mug from Nicki for my grandma some years ago.
The mug was obvisiously white white a pastel orange print on it. It had sheep in the typical Nicki style on it. One was the grandma with glasses on and the smaller sheep where the grandkids and the grandma-sheep held a big ice cream cone with 2 different ice cream scoops in it and they where all licking the ice cream and it read in German "Beste Oma" (best grandma). I also bought some chocolate that came in stick-form wich makes it look elegant and pricy and the store also had a free service that if you buy at least 1 item they will wrap stuff as gifts for you so I asked them to pack it in a seetrought foil with a bow on top.
Try that. Get her a mug that you think she will love (or a specific type of mug if you know what drinks she preffers) put some fancy candy or her favourite candy inside and wrap it nicly.
What else you could do is getting a fancy looking jewlery kit, make a neclace or bracelet from it and gift it to her. I did that also 2 times for my mom's birthday as I was 13-14 and she loved the necklaces a lot. For this you need a thin metal string, small silver beats that you can press flat with pincers to secure the ends of the string and than put some nice glas pearls on the necklace or bracelete. One thing that is also nice is the clasp where you have a round object and put a metal-pin on it to close the bracelete or necklace since this makes it easier to open and close the jewlery (especially usefull for people with big fingers or long nails)