I think you are doing all the right things with her!

At three months they will think a shadow on the wall is amazing so don't worry too much about trying to stimulate her. Don't stress about leaving her on the floor for a kick while you're in the shower either, enjoy it before she starts rolling and then you have to worry about where she's rolled off to

By the time the weather starts to get warmer then she will be at a great age to really take in things when you go for a walk