It's not a big deal
The incorporation of elements from Michelle Obama's speech at the 2008 Democratic National Convention into Melania Trump's speech at the Republican National Convention does not have the makings of a major scandal.
Trump staffer Meredith McIver has taken responsibility for the incident and has apologized. Ms. McIver describes a phone conversation with Ms. Trump, "She read me some passages from Mrs. Obama's speech as examples. I wrote them down and later included some of the phrasing in the draft that ultimately became the final speech. I did not check Mrs. Obama's speeches. This was my mistake and I feel terrible for the chaos I have caused Melania and the Trumps as well as to Mrs. Obama. No harm was meant."
We in the press are sensitive to using material without appropriate attribution, which we should be, but Ms. Trump and even her speech writer should be excused for this minor error in judgment.