
80+32(+32)+40+35+(50 or 55, depending on final item).
That's 139-171 base AD+200-205 bonus AD, plus 1250 HP that she normally wouldn't have with the bad glass cannon builds used.
That 1250 HP makes Titanic do 38-122 bonus damage, and 367 for the active.
In addition, you get a ~940 HP shield that synergizes very nicely with Death's Dance.
The fact that Riven's passive+Q have total AD scaling means that the glass cannon build you're talking about is inferior in every way.
TL;DR:
She can't do any sort of impactful damage at ALL if she goes even slightly tank
Is a bullshit statement.