Wouldn't it be better to simply use N.N. of Namur as name for this lady.
The study of Hans Vogels from which her parentage is derived clearly states:
Haar naam is niet bekend maar wellicht heeft ze [Ermengard] geheten naar de moeder van graaf Albert II. Laten we voorlopig maar van deze hypothese uitgaan.
In English: her name is not known but she might have been called [Ermengard] after the mother of count Albert II. Let's stick with that hypothesis for now.
As far as I know geni policy says that a hypothesis should never be presented as a fact. The name Irmgard/Ermengard clearly is a hypothesis. So my suggestion is not to use it on geni.
In fact, it is not 100% certain that the wife of Herman van Malsen was a daughter of Albert II of Namur and Regelindis of Lorraine, so if you are looking at this academically then the link between her and her parents should also be broken...
I will see if I can translate the full text of the excurs of Hans Vogels in English, so that it can be understood by non-Dutch speaking members as well