I am doing some work for this person, she has a Mac and I have a PC. When she sends me attached files a useless htm file is always included as an attachment. So I get the real file and one useless htm file.
You sure it's not just the software she's (or you) are using? I seem to get a lot of extra files from people who send me attachments. I just ignore them. I've never opened them to see what's inside them though.