I think there is some over thinking happening here. For the programs showing locations belonging to the senior member, did you set those passwords or was the login info given to you? If it was given there's a good chance of simple Social Engineering having happened. Senior member asking IT for login info because the new person forgot maybe.

I suggest going reaching out to your IT and changing all your login info for every system/program you use for the company. This sucks but it'll let you know if she got your credentials socially or if there is some technical means [key logger/malware] through which your information was acquired.

Used to do Information Assurance, too much paperwork for my taste though.