Every romance manga about young people ever pretty much has a fantastic wing-mom in it. Rooting for it, helping just a little from the shadows. But here she is at least, boys and girls. The antithesis to that.
If it doesn't show that she was, in fact, dragging this girl off to interrogate her about the relationship out of excessive interest or something, then we have a manga mother that is so dense she would actually do this with no ulterior motive at all because clearly they're just friends and she wasn't interrupting anything at all.