But in her defense, she mentioned that her team just went thru a big restructuring and, during that process, she lost her major projects. Then she was moved to another area, where she is doing a type of work she hasn't done in years. Clearly, she feels her position isn't very secure under the new management.
Maybe if her job situation felt secure to her, she wouldn't feel so nervous about taking on the receptionist responsibility.
I don't think she is saying this out of arrogance but out of fear and frustration that it could be sabotaging her career.
Also, some of this depends on company/organization size. In smaller orgs, ppl filling in and wearing multiple hats as situations merit, is typical. In larger orgs, there are more clearly-defined levels of responsibility that employees generally don't cross. (At least that has been the case iME.)