Hi Bookbox.
Yes, I see what you mean about it probably not being London to Melbourne. That also casts some doubt on my idea that Marion was in England in 1879. Some background:
This dedication comes from a book of poems started by Marion's aunt, Elisabeth Mead, in 1842 when she was 12 years old. An inscription in the front of the book has Elisabeth's name and that year on one page, and on the opposite page is Marion's name and the date 13 May 1879. It appears that Elisabeth probably gave the book to Marion for her to continue writing poems in it, though exactly why she chose that time I don't know.
Marion was born in Keilor (outer Melbourne suburb) in 1857 or 1858 (birth certificate is not in Victorian records), and she would have been 21 in 1879. I've assumed that because they were a wealthy family Marion might have done a "grand tour" to the Mother country but I'm probably wrong.
There is some evidence that Elisabeth (who came out with Marion's family) was in England in 1871 (Ancestry information, which I'm not 100% sure is accurate), although it would (to me) seem odd that she would return to Australia some years later as she evidently died in New South Wales in 1911.
Given your clearly correct observation that it's not "from London to Melbourne", I'm going to have to re-think Marion's movements and precisely where and when the book was given to her.
Many thanks for your response.
Peter