My baby is 4 months old and she starts to watch TV as soon as we switch in. Even if I make her lie down with her head opposite to TV then also she turns and somehow manages to watch. Is it safe at this age for her to watch TV and if not then how to stop her from watching.

the easiest way is to watch tv when baby is sleeping :)

Screen Time: How Much is Too Much?

Right now they can't see anything clearly, so don't worry. They are just curious to know what's moving.. As she starts growing you can keep her off the TV by spending time with her or engaging her in some activities. It's in your hands, if you are going to watch TV in front of her and ask her to play with her toys it's not going to happen.