Hi yall! I need some advice about how to get an orphaned kitten to being accepted by my current foster who is just recently a mother to her 3 kittens (they are 3 days old).

My mom got a call from the shelter about an abandoned Calico kitten who looks to be a week old (eyes are not open and based off of weight and how big she is they estimated it’s a week).

Mama is very very sweet and is very friendly with my mom and loving, and I would love some advice how to get her to accept this foster as her own