Ever realize this:
Ghoul School came out in January 16 of 1988. That's 29 years ago.
Now, Winnie's age isn't stated, but let's estimate and say she's between 6 to 8 years old. Adding all that up, the gal's someplace between 35 to 37 years old. She's either a MILF and a half at that point, or a damn well old Christmas Cake that's never had children. She's probably older than over half of the people in this thread. Of course, werewolf years can be a factor too, so who knows how that works exactly. She could have a life expectency of several hundred years, thousand(s), or the same as any human. Regardless, she's pretty old at this point.
Of course the others aged too, Sibella being in the 8-9 range if I had to guess, Phantasma around the same range as Sibella, Elsa 9-11, and Tanis 4-5. But that's ignoring their undead qualities. While you can excuse Elsa somewhat due to the whole "is she really alive or just an undead flesh costruct" problem and toss her in with Winnie, the others are straight up dead. Sibella being a vampire though, she's most likely exactly the age assumed earlier, to which she will grow until she hits her prime and age will no longer physically affect her. Tanis and Phantasma are all sorts of weird. Phanty is really wonky to try to explain other than just handwaving it and saying "Fuckin' ghost stuff happened." As for Tanis, gotta establish this: you could say Tanis got mummified, then woke up like a time capsule or freeze pod. 1000s of years may have passed, but she's still only been out for about 4. So she will still age mentally normally, but without some magic bullshit to affect her body, she's stuck as is physically.
Put way too much time into thinking this post. But yeah; your GS waifus are fuckin' old.