Yeah, that relationship is actually worrisome for a variety of reasons despite the surface-level cuteness. The age gap is troubling, definitely, since it's been established that the ghosts don't mature physically or mentally in the dream bubbles (in fact, the longer they've been there, the more stunted and trapped in their mentality they've become).

Plus there's the fact that Meenah is pretty much the only one Vriska has, and Vriska is afraid of being alone. So she's behaving like a sycophant and trying to mold her entire personality around Meenah -- her pattern is becoming obsessed with something or someone and then modeling her personality off them. (Mindfang is the most obvious influence, but there was the fairy thing with Tavros and her Nic Cage fixation when she was interested in John.) Even if the age gap isn't a big deal in troll culture or whatever, I don't think Vriska and Meenah are equals in this relationship -- and that kind of balance HAS been established as important, even in troll relationships.

So, I don't know -- I think Hussie probably had these issues in mind when he paired Vriska and Meenah up. The relationships between the characters in Homestuck tend to be pretty complex, and sometimes downright unhealthy.