I'd hoped this may have died and gone away on its own, but it seems that "Melanie" (or whoever she or he really is) is a persistent little scammer that's working hard to screw you over. I've seen this email appear in various clients' inboxes. Always exactly the same format with the site URL changed and he/she uses slightly different names, but the scam is always the same. Get some poor sucker to click on a link to "check out a document listing supposed links to images which are copyrighted". There's a linking to a Google Site. I don't know what's at the end of that, and, frankly, I don't care nor have the time to bother finding out. But you can guarantee it is NOT a list of copyrighted image you are using illegally.
Shock! My site is using copyrighted images illegally!
Don't get me wrong, using copyrighted image without permission is WRONG! 100%. And it CAN cost you money if you do it and get caught. That's why we are carefully about where we source images to ensure they're legit.
But back to the email...
It starts off legitimately sounding. Some poor, hard-working photographer is upset that YOU used HER (or his) images on your site without their permission. I'm with her/him so far. Then they forget their English with " It's illicitly to use stolen images and it's so mean!" Well, OK, you don't need good English to take a photo, right. And, we did, after-all, use their photos illegally. Let's cut them a break.
Now the link to a supposed document containing links to her images for "evidence of my copyrights." DON'T CLICK THIS LINK! You have been warned...
Now she/he starts pouring on the heat, stating they'll write to your hosting provider (who, generally won't give a rat's behind) about your alleged infringement. If that doesn't work "... you may be pretty damn sure I am going to report and sue you!" Funny, I thought she/he said in the previous sentence she was going to report you. Maybe she'll report you again, or to someone else. The general degradation of tone and language, along with the bad English, and zero evidence (in the email) of any infringement should send your scam-alert antennas into overdrive.
Bottom line: Delete it. Don't follow the link. You can try emailing her/him back, but it will bounce (yep, I tried) or phoning her/him, but it goes to some other poor sod who's probably REALLY ticked at the gazillion calls they're getting.