mandibrandybuck, who wants to be an artist, decides to go to the library to work on her artwork and gets offended by the fact that some random mother doesn't recognize her OMGSOEXPENSIVE colored pencils!!
see here now i FULLY agree the parent was lazy and should not have asked the OP if her kid could sit with a total stranger while she went to do her research.
but ya know, if she didn't want to invite the possibility of this happening, maybe she shouldn't have allowed the parent to "ask" if the child could sit with her, much less offered the kid a piece of paper and regular pencil. that's just asking for a parent like this to ask for the oh-so-precious Prismacolor pencils. a simple "i would rather not be responsible" would suffice and not make her look like the rabid child-hater she probably is.