Going by the pixivpedia entry, it's really just feelings of motherhood coming from a younger woman, rather than one that's old enough to be a mother. There's nothing really sexual about it.
Ikazuchi's even the page image! The ur-example it gives is Lalah Sune towards Char. The term /habumi/ comes from /habu-/, the sound that a baby makes, and from adjectives that end in /-mi/, hence it's somewhat like 'inducing a baby's babbling' - i.e. they're mothering so you go into baby-mode. (The entry also cautions that this term is inappropriate to use with lolicon and baby-play things)
Not quite sure where the original translator there got their info from.
GroooowlHuh?Ughh...Hungryyy-...Ikazuchi...!You can have this onigiri if you'd like!I can feel the motherly love...The word she's using is a slang term somewhat similar to 'moe', specifically in the context of a younger girl acting motherly.Warspite-san, where did you pick up that word...I'm famished...Was that not the right way to use it?Well, no, you did use it right, it's just...You okay? Are you hungry?But Eugen taught me how and everything!Pffft
