It turns out her son Reggie has several medical conditions and needs to be fed through a peg inserted into his stomach.
"I think it is disgusting how people can judge too quickly," she wrote. "Pushchair, walking, wheelchair whatever is used you should never ever judge anyone!! I feel so sorry for anyone who has gone through this themselves."
She said medical disabilities are "not always obvious", and that she hoped the writer would see the post and learn that.
Ms Gearing also said she wants her response to go viral. It's received over 100 shares on Facebook.