Sentence:  ... I wish anybody could give Mary a hint that it would be a great deal better if she were not so very tenacious, especially if she would not be always putting herself forward to <WSD>take place</WSD> of mamma. Nobody doubts her right to have precedence of mamma, but it would be more becoming in her not to be always insisting on it. 
Meaning of the word marked with <WSD> tags:  To take precedence or priority.