The short answer is: probably not allowed.
Copyright matters are, unfortunately, almost never very simple. We can't see a legible image of the clipping or read the citation you included about the source for it because the privacy settings on Myrtle's profile prevent it. But given that she died sometime in the 1990s what is clear is that there's valid copyright protection in effect.
Somewhere. We just don't know where. The obit could have been written by a family member, by the funeral home, or by a stringer at the newspaper. Whoever actually wrote the obit has the copyright. If a newspaper reporter wrote it, then it was probably a "work for hire" and the newspaper has copyright.
To complicate things further, we can't see where Myrtle died and so don't know where the obit was written, but laws differ somewhat between countries. Her parents died in Canada, so if the obituary was written and published in Canada, the copyright jurisdiction would be Canada. Title 17 U.S. Code and precedents that have resulted from court cases in the U.S. won't apply...and of the 5% I know of copyright law, that makes up 95% of it. 
If you're uncertain about the authorship, copyright status, and provenance of the obit, the safest bet is not to post an image of it. The information contained within the obituary, however, can't be copyright protected, only the actual written article can be. So you could certainly restate the relevant facts (leaving off names of the living, of course, since naming them would run counter to WikiTree privacy policies), include that text in Myrtle's biography, and cite the details of the obituary as published in the newspaper.
