Without fail, the best website on any messenger is that messenger's official website (if he or she has one). In the case of Marie-Julie Jahenny, the Breton stigmatist and end times messenger -- in whom her local bishop was a staunch believer -- it is: https://www.marie-julie-jahenny.fr/
This is hands-down the best website on this peasant and prophet. It is focused, simple, and most faithful in presenting the amazing story of this modern mystic, who is more relevant now than in her own day since we are living in the end times. Check out this website: its only drawback is that it is mostly in French, but there is plenty of great information. This introductory page on her is the most important; click here:
There is an authoritative book (and important end times religious items related to her) here: https://www.marie-julie-jahenny.fr/religious-items.htm
If you have difficulty ordering that book by clicking here: https://osmm.org/sample-store/marie-julie-jehenny-the-breton-stigmatist/