Peek a boob?

So my almost 4 month old started playing peek a boo with me on her own while nursing. She starts eating for a bit then looks up at me, waits for me to smile, smiles back at me, then pretends to nurse and repeats the whole thing.

It’s pretty freakin adorable and makes me laugh, but I’m not sure if it means she is done eating or if this could affect her weight gain, and whether I should stop her.

I’m inclined to let her continue because it’s fun for both of us but I just don’t want it to create problems. She’s already petite (4th percentile) so I’m scared of her not gaining enough.

For your help, here’s a pic of her. Also, just cause she’s so cute and I adore her so much.