it seems that Excel file transfer between a Mac and a PC, (and vice versa), is possible, as long as you are transferring between compatible Excel versions. I saw this at a web site, (link below);

"Save your Excel file in a format compatible with the other person's version of Excel. Excel files are compatible as long as they are the same version or greater. All Excel file types are backward compatible with older versions of Excel".

Now the problem is, is your PC 2010 version of Excel the same version as the receiver's Mac version of Excel 2008. I don't know.

So, try this. Ask the receiver to send you a bog standard Excel file from her machine in the normal file format she uses. EG, if she sends you a file in .xls format, and it opens properly in your version if Excel, then you know that she should be able to receive your own .xls excel file version.

It might need a bit of experimenting to get it right.

Shame its not Word. The answer there would be Rich Text Format, .rtf . Happy