There is at least one online Catholic book store that refuses to sell the Pieta prayer book for the sole reason that it contains unapproved private revelations from Mutter Vogel. There is no reference either in the Old or New Catholic Encyclopedias to Mutter Vogel.
One can judge the inclusion of so many references to Mutter Vogel in the Pieta prayer book and decide that Mutter Vogel should be taken seriously. Conversely, one can judge the inclusion of so many references to Mutter Vogel in the Pieta prayer book and decide that the Pieta prayer book is dangerous to one's spiritual health because her private revelations are being presented as if approved by the Church.
Our recommendation would be to find another prayer book and to judge anything attributed to Mutter Vogel as little more than pious reflections that should be approached with great caution, if not avoided altogether. It doesn't take a lot of poison to undermine whatever good might be found in private spiritual reflections. Mutter Vogel's revelations have not been approved by the Church, and that should be a sufficient caution to any faithful Catholic. There are vast numbers of approved spiritual works. Draw water from those wells instead.