[quote=@Crimson Flame]
<Snipped quote by Double>

<Snipped quote by Guardian Angel Haruki>

So Vicious Mockery would probably take the other spell slot.

[s]This makes me relieved she’s a Sea Elf and not a Triton.[/s]

[/quote]

Oh no. Vicious Mockery is a cantrip, so that won't take a spell slot. 
Ariel can use Cantrips as many times as she wishes. ^_^