Being married to Dunbar at age 6 is possible, as is the birth of their son Alexander in 1373, but it doesn't tally with the stated marriage in 1356 to John / Eion Mor "Good John" MacDonald, Lord of the Isles
There were bigger problems in that tree than an "off" (but hey! Sourced! Not a geni error!!) birthdate.
The first and a big one was separating Marjorie, Princess of Scotland from her sister Margaret. Then worked on the rest of the siblings. Should look a bit better now.
I don't have a greatcsolition to the birth date issue as its in line with her sibs. The marriage date is validated as cited by Crawley.