Can someone know exactly when am I using my iPhone?

I have a friend that that can see where immediately somehow when I pick up my telephone and start using it can pick it up as I wake up and immediately she will start texting me or in the middle of the night if I wake up and can’t sleep she starts messaging me. How can she say that I am on my phone and how can I change it to where she cannot see that I am on it I have a iPhone and it is driving me crazy because I can’t figure out how she is seeing this to do sometimes is just pick up my telephone

[Re-Titled By Moderator]