She's probably just experimenting. She is learning new things all the time and is probably just interested in how it feels. She will likely grow out of it soon enough. In the meantime, perhaps try some tactile play so she can start to experiment with how other things feel. Water play is a huge hit with kids, they love it and it is also really good for their development as well as being very calming. Sand play (mind she doesn't eat it though!), a touch book of different materials and textures, etc.

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