Pretty sure it's safe to assume any girls on discord are going to be minors.
Discord (2015) is probably gen alpha's equivalent to facebook (2008), myspace (2003), AIM (1997), and IRC (1988).
The oldest native discord users (have Discord as their first messaging platform) would be 16 right now.
Looking at this now it might be worthwhile to focus on creating or finding the new platform for gen beta as Discord (like every other messenger) gets accusations of creating a space for pedophiles as late adopters, typically older people, start using the platform too.

Edit:
Honestly looking at Wickr right now and it being released 6-8 years after Discord might mean that it is a messenger that gen beta/late gen alpha would use because there are very few older people using it. Not sure but looks bullish so far.

Edit 2:
Nope looks gay and made for businesses.

Lol all of robert's alts are online