So she has to be older, but not twenty years.
I don't think she looks 20 years older either, but I do think (or remember thinking) she looks older.
But in-game--MC knows Skylar well enough to have seen her naked. Now suddenly she's a couple of years older. Do you really think MC isn't going to notice that? Players, OK, maybe not (we won't, if Jestur doesn't change the model other than the ink). But the characters? IRL, you often won't notice two years' change in someone, because it's gradual over those two years. But to see that in a week? I think you're going to notice. I guess a counterpoint could be that whatever changes happened by two years of aging would be overshadowed by the ink?
I think it's pretty strongly indicated that Skylar has traveled in time, and what we see doesn't fit her having traveled in the same way as MC. I can imagine a few ways this could have happened:
- She went away (different physical location, but no time travel) for a period of time (I'm going to say about a month, but that's mostly a place-holder--but at least long enough to have gotten the tattoos, obviously), then time-traveled to a week after she left, and gets back together with him.
- She time-traveled to some other time, spent a month (or whatever) there, then time-traveled back to a week after she left.
- She time-traveled to some other time and hasn't yet (in MC's timeline) returned. The Skylar that returned is from at least a couple of years in (her, maybe MC's) future.
- As above, but she traveled in space, not time. In this one, there are two Skylars present somewhere in 2019: one (I'll call her 2019 Skylar) has left the immediate area (her whereabouts are unknown at this time), and another (2021 Skylar) who's in MC's neighborhood.
- As perhaps a variation of this one, she just went away for a couple of years, and then time-traveled back to a week later and gets back with MC.
- "Our" 2019 Skylar has left (temporarily or permanently), and the Skylar that "comes back" is from some sort of parallel universe.
Apparently Dark, which is said to have heavily inspired Ripples, includes elements of parallel universes, so I wouldn't rule out the last possibility, but it'd be something we haven't seen yet (at least, not clearly). The third or fourth sound like where you're at (except that in the variant of the fourth, their first time is still the first time for both of them), and again I wouldn't rule them out, but I think MC's going to notice that Skylar's suddenly older than she was last week--possible distractions (i.e., to keep MC from noticing) would be the ink and/or "hot naked girl." I think the first or second are the simplest and therefore most likely to be correct.