Help With Multi Author signature

I have the plug-in DDAddSig I use for automatic signature on every post at the bottom. Now I have another contributor and would like to assign my signature to only posts I write, and add another signature to display on posts she writes. Does this plug-in do this? (I keep seeing that it does, but cannot figure out how to do it.) If so, I need help in makeing that happen. I have both signatures as .jpegs, so all I need is to find out how to assign the signatures to the authors. Thank you in advance