Quoting Doodlebuggy:“ What is copyright infringement? As a general matter, copyright infringement occurs when a copyrighted ... [snip!] ... work is an expressive creation that includes major, copyright-protected elements of an original, previously created first work.”
Momma in 2010 I would suggest making a facebook page or website and advertize that way
you can still link your hats here, you just cant openly post those for sale on bg. I highly doubt sesame street is going to come after you for trademark infringement BUT mara just doesnt want it openly advertized on bg just in CASE something ever did happen. she could be liable for it.
if you have any questions about it feel free to pm me!