4 months old!

I can't believe McCall is 4 months old already! She has been such an AMAZINGLY HAPPY baby, and has brought so much joy to our home. She is our little tank!She almost sleeps through the night and hardly ever cries. That is a lot in part to this little habit...
She can't seem to make it through the day unless she is sucking on those two fingers. She REFUSES to take a Binky but will go peacefully off to sleep as long as she can have those tasty little fingers in her mouth. There have even been times when she is nursing that she tries to wiggle her fingers in to her mouth instead.
Am I a bad mother because I let her suck on her fingers?

She always has a smile on her face (except when she hears Kailey coming, then it is more of a wince). She loves to sing and coo. She is getting really good at holding her head up during tummy time (unless she finds those fingers, then she is content to lay her head on the floor and just munch away at them). She has started to giggle and laugh when we tickle her or nibble at her neck. It is the sweetest sound ever! I will see if I can get it on film. She has a doctor appointment next week and I will have to post her stats. She is our little calm and content baby. It has been a welcomed change from Kailey's energy. I think McCall takes more after me ;)