the maker may have pressed the blocks...heat setting the lines without meaning to, which is maybe why she sold it?? could we see pictures of what it is you are trying to deal with? maybe we could offer some more help if we saw it.
was it a design the maker drew on the quilt top or was it pre-printed? if it was pre-printed and pressed (heat-set) they are probably there to stay. if they were drawn on with a pencil you could possible pre-treat with a stain remover...like shout applied directly to the lines...it really depends on what the marks are made with.