Creepy or normal?

My sister whom I love so dearly has been TTC... she LOVES my daughter like crazyyyyy!!! You should see the way she loves on my daughter and spoils her... but, what I have been noticing is that my SISTER tells my daughter to call her mum. Another thing is, myself and my sister will be with my daughter and my daughter will call out for mum and my sister will run to attend to her and say “yes baby, I am here”. She uploads my daughter’s pictures everywhere on social media and say that’s her daughter- cute right? But all these things are creeping me out

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Sorry for the typos, I typed that in a rush