How can I deal with someone at work who I feel is overstepping boundaries?

The background:
I work in an office where my position involves a specific area of expertise (ie. mine is the only position of its kind in the office and involves technical knowledge that others in the office don’t need or have). My job description is very defined and unique.

A co-worker has recently started some behavior that is angering me and I just don’t know the best way to handle this or even why it is bothering me so much. I’ve worked with this person for 2 years and although I’ve never particularly liked her, I’ve been able to peacefully coexist because our roles are very different and we’ve never worked closely together.

Recently she has started the following behavior:
– proposing projects that overlap into my area of expertise without ever consulting with me (ie. she comes up with the bright idea but I’m the person who would actually have to implement it)
– discussing these projects at meetings with all of our colleagues without ever including me in the meetings or even telling me about the projects
– telling my supervisor and other supervisors in the office that they need to hire another position like mine because I’m overworked
– telling my supervisor to change my job description and responsibilities so that there is more time for me to work on implementing her brilliant ideas

I feel she is purposely going around my back and talking to everyone in the entire office (including my supervisor) in an effort to gain support for her projects and ideas and it seems to be working. I’ve been trying to stay calm but I feel that at this point I have to do something to stand my ground and let her know that she is overstepping my boundaries.

The thing that bothers me most is the way my supervisor and other supervisors have behaved. It’s like they are brainwashed by this person. They’ve listened to her ideas, given support in the way of resources, while never telling me about these projects until recently.

I at least want to start by letting my supervisor know that I’m offended that I wasn’t included from the beginning and ask that I be included from now on. I think my manager had a responsibility to include me if she knew all of this was going on.

Am I crazy? What would you do?