She lets me touch her a lot. Is this normal?

I have a colleague with whom I am getting too close in touches. Initially I used to put my arm around her shoulder. Our thighs brush and remain in contact when she sits beside me. She lets me place my hand on her thighs and her back just above her hips. I can also hold her waist and even grabbed her playfully from behind. Is this normal way how girls behave with guy friends? Please suggest me how to proceed.
She lets me touch her a lot. Is this normal?
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