No mention of Mass Effect? There are aliens but not really monsters. (Well, depends on how literally you're defining "monster"; ME3 also has some online content but it can be avoided.) Borderlands. Highly violent and there are monster-like spiders but most enemies are humans (also not much of an RPG nor even really sci-fi, maybe a "low sci-fi" just as there are low and high fantasy genres). Deus Ex. System Shock (it's older; monsters).
There is definitely a distinct lack of sci fi RPGs.
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I find it very curious that "fighting" is not restricted, but "magic" is, and yet sci-fi is allowed. The "fiction" part of sci-fi is often indistinguishable from magic, insofar as it breaks the laws of physics and any explanation to that effect may as well simply be "magic." It is not a case of the oft-quoted "any sufficiently advanced technology is indistinguishable from magic," but rather that in a strict examination, there is little distinction between a mechanic described as "magic" and a mechanic described as "impossible technology"; rather that these terms imply much more about the setting than the mechanics used within them. Who is to say, for example, that the "magic" of [insert something] is not actually resulting from a technological source that the in-story lore has simply forgotten about, despite retaining the ability to exploit it?
(I don't suggest pointing this out to your mother, presuming you haven't already recognized that fallacy yourself.)