I am sorry to hear you are worried about your kitten still suckling. I am a veterinarian and will do my best to help.
Some kitten, whether weaned early or not, will continue to try to nurse on blankets and sweaters. Since your kitten now has an actual "mother" letting her nurse, she may continue to do this. I once saw a year old cat still nursing his mother! The Ragdoll, even though she is spayed, may even start to make milk.
I would try to gently discourage this. When you find them doing this, I would try to redirect them to food
, treats, or by playing with a feather, fishing rod type toy, laser pointer, etc.
You could put a sweater on the Ragdoll,to cover her nipples. The poor thing probably won't like it, but I would try to break this habit.
Let me know what else I can help with or answer.