Yorkiegirl, dd (19 months) occaionally also gets a bit of discharge just like you describe and has done since v. small. I haven't ever had it checked out but I'd imagine that if it's not smelly, she's not sore, it doesn't become more or worse, and otherwise she seems well it's probably nothing to worry about.
When you say her nappy was 'clean and dry' this morning I take it you don't mean literally dry? That would be a bit worrying in a 6 week old after so many hours ...