"Breast friends" she cheekily captioned the sweet pic.
And Shay's fans are loving the strong, sexy, feminine photo, taking to the comments to praise the 32-year-old.
"I love it! Normalise breastfeeding," one fan wrote.
“Love this and I love all the photos of celebrities breastfeeding. Paving the way for the rest of us mommies who are not in the spotlight. #NormaliseBreastfeeding,” said another.
Shay recently spoke out about being a mum and said that she has really been enjoying taking a step back for her daughter.
“I find myself being a lot more present, and I’m just looking at her every single day. You reflect on how fast time passes when you’re forced to slow down,” she told Vogue in November.
“The surprising thing is how much I enjoy this calmness.”
While back in October, shortly after announcing the birth of Atlas, Shay was mum-shamed after she left her little girl to attend a party.
One of the comments visible in her video read: “Mother of the year award right here!!!! As if you seriously could leave your baby to go party?!!! I hope the child’s aid look into this and your abilities to be a good parent cause damn!!! Lacking some serious skills there [sic] sweety! #selfish.”
The You star then went on to clarify a few details to fans.