Maybe like I did this longhorn, traced from a template with food marker, then went over that with RI and filled in?
Not sure this is it, but she may (only 'may') have piped it separately on wax paper or food-safe acetate and then dropped it onto the red flooded RI. I did this with my Chamber of Commerce cookies and my soccer balls against the green background and it worked like a charm. The only trick would be making sure the heel didn't break off.
However, my guess is what Shiney says, but I thought I would throw this out there as well.
Did you try PM-ing her?
Thank you so much for your comments. I did pm her, hopefully she will respond.
she probably outlined the stiletto with black, then filled it in and let it dry as well as the outline for the heart.
When it was dry ( or at least not as wet) she flooded the rest of the cookie with red RI or maybe color flow.
HTH but id go straight to the source.
P.S. yes! her cookies are precious!!