Thanks for your input. I was hired about 2 months ago and it was made clear to me several times that I would work on this project but I believe this other person felt threatened by me and wants to take over the lead because she owns the system . However, I don't think her skills are there to do the work.

Every company has its own culture and way of getting the work assigned and completed. There is a dynamicat work.and it is built over time. It sounds like in your excitement of your new job and wish to contribute, you may have hijacked the process without realizing it. So while you have the expertise that doesn't mean charging ahead without a clear idea of what your role is on any given project. Learn from ithis and try to take your cue from the manager and your peers on how they relate and how to contribute your talent. No need to dumb anything down or hide your skill just spend time understanding how and when to make yourself useful. Get to know your team and the group dynamic.

It feels like there is context missing from this story. How recently did you join this company? Were you assigned this project, or did you begin working on it on your own initiative? Did you discus it with your boss or with the colleague who "owns the tool"? Are you familiar with what has been done until now? What is your expertise, how does it differ from the knowledge and experience of those already on the team, and are you offering it to support the team or to promote yourself in a new setting and to stand out? It sounds (based on the information in your post) as though you startled your boss in front of others by announcing progress on something she thought someone else was working on, and she could have reacted better. If you're really interested in working on this and think you can make a positive impact on the project, it is worth having a conversation with your boss to explain your position (why did you assume this project was yours? What others owners are involved? ) and explain that, based on your experience, you think you would be a good person to work on this specific part of it, perhaps together with the colleague your boss mentioned as the owner. The company hired you for your skills, so they will probably be happy to have you apply them effectively, but there may also be history that you are not aware of. "Withholding your expertise" because you feel admonished is probably also not helpful (and, again depending on context) can look like sulking; how can you offer your expertise in such a way as to help, and work your way into the project, rather than just taking it on?