If she's not into couples activities and you're home with the cats while she's out doing things, what relationship do you two have? What do you do to remain connected? This would be an issue whether polyamory were in the picture or not.
Hopefully the issue of her wanting to see someone else will inspire you two to work on strengthening your own connection rather than it just being part of the process of you growing farther apart as she gets wrapped up in New Relationship Energy.
I would personally want to make sure I felt very secure and fulfilled with my partnership before either of us branches out with other people, and it doesn't sound like your needs are being addressed very well at the moment. Of course, your message was brief and maybe this is just a fleeting feeling and you're usually quite happy with how things are going. If that's the case feel free to correct me.
ps: I haven't even addressed the potential issues of her dating a co-worker, if that's what you mean by "someone she's working on a project with".