Babies at her age are easily distracted because nursing now means sitting there for 10 minutes doing nothing. It can be boring as compared to crawling or trying to stand or even drinking from cups.
It can be mistaken as a sign of weaning but is usually not as weaning occurs from 18-24 months.
Try to increase your milk supply(with milk boosters or power pumping), offer breastmilk first then solids, and no sweet drinks.
You can also engage your baby during nursing by singing or talking, playing finger games or giving her a toy to play with (she may not like the necklace).
There's a lot of relevant information here: http://kellymom.com/ages/older-infant/babyselfwean/
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