You can never go wrong with a Pendelton blanket. Make sure to choose something with a really meaningful design. If she already has a blanket, there are Pendelton purses and other accessories she would love to receive for Mother's Day.
Cradle Basket or Cradle Board
It doesn't matter if she is a new mother or a Grandmother. The gift of a cradle basket or cradle board is very special. If she is about to become a new mother she will have a new heirloom to pass on. Many women like to collect these and place dolls inside of them. Just make sure that you get the right style for the right person. Where I come from, it is important to keep the cradle board laced and tied. Otherwise, you might signal the spirits that you are ready to have another baby to put in it.
Some women like jewelry that never comes off. Let her express herself with a tattoo. Before you buy her this gift, be ready to pay top dollar for it. You don't want her to have a low quality, prison budget tattoo forever. Look around. Find someone with experience tattooing dark skin with bright colors. Find someone who has done a considerable amount of tribal or Native tattoos. Neither of you will regret it.
This isn't your daughter's dance shawl or your grandmother's, "I'm cold" shawl. This is a shawl made especially for mom to wear to special occasions. There should be colors and appliques that represent her personality, things or people that are important to her, or how she makes you feel. She will have this shawl to wear proudly to gatherings, feeds, and other Native events with pride.