I need advice on how to politely put my friend in her place...?

Three years ago a friend of mine needed someone to babysit her son. Her husband creates websites and I needed someone to create on for my photography business, so we agreed we'd trade babysitting for my website. Well, three years later I still don't have a website. I only babysat their son for 6 months, but I still held up my end of the bargain. I've been extremely patient about getting my website done, but I can't have a business without one. This fall I did family photos for this couple and they never offered to pay me, which bothered me, but I never said anything. A few weeks ago, they asked me to do photos of his sister's baby shower. She had the nerve to ask for the "friend discount" which meant free. So I told her how much I would charge for a baby shower and included the "friend discount" of 25% and I offered to give her TWO album proofs instead of one. Today she told me she thought I'd do it for her in trade for all the computer work her husband has done for me. Am I wrong in being pissed off? I still haven't recieved anything for the last thing we "traded". I wrote her an email stating we "traded" babysitting for my website, but it's taken three years for her husband to finish it, I just haven't hit send yet. How would you put her in her place, but still not come across as a total *****? Any thoughts would be great. Thank you in advance.