Melania Trump will make a fine first lady, essentially because the role of the first lady is more show than substance and requires no experience. To that end she fits the bill. First lady duties are not rocket science, and are more for putting a good face on the ugliness that permeates politics.
Melania Trump is a very wealthy and privileged lady. She has grown up in a life of luxury, and is not known for anything more than being Donald Trump's wife. I do not believe she would have much to contribute as a first lady. She does not seem to be passionate about any social or women's issues.
No, Melania Trump would not be a good First Lady because although she speaks several languages, she failed to graduate college and will fail to connect with the American people because she is a first generation immigrant. Melania Trump's past history as a model who has posed nude in magazines will also come back to haunt her if she becomes First Lady.
I don't think Donald Trump will make a good President and by extension I don't think his wife will make a good first lady. The President of the United States not only leads the country, he in effect leads the world. Mrs. Trump has never been in any position akin to that of a first lady, so there's no way she'll be good at it.