Correções

My line manager asked me whether I need help from my peer, who reports to the same manager like me. I rejected.

I thought that will cause some troubles about this project, such as who is owner of this project and will she obey me?

At the end, my line manager told me that she had known how hard- working I was on her pregnant period and the project had gained higher performance, but due to thinking about another peer's feeling, she can't recruit an intern to support my work to reduce my workload.

My line manager always tries to treat every subordinator fairly.

But she ignores it's unfair for the hardworking/excellent staff.

That will cause the hardworking/excellent staff tend to be mediocre workers or leave company.

Do you agree with my opinion?