Wtf? should I be worried?

I have a one year old. My mom has been having her suck on her breast for I don't know reasons. Now my child can’t sleep without sucking on it. The only reason I’m aware of this is because when she gets fussy she starts touching my mom breast and every time my mom acts dumb as why my child is trying to have access to her breast. Is it something I should be worried about? I work night shift, I’m pretty sure she lets my child suck on her breast when I’m not there. The nights that I’m there she acts like she doesn’t know why my child wants to suck on her breast.
Wtf? should I be worried?
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