Tell that to Nu Beetle. His last book dragged itself over broken glass all the way down to 10,000 in sales. DC deliberately kept it going despite declining sales, all the way down there. And, despite that poor showing and subsequent cancellation, they still relaunched his book in the DCnU.
Of course, Stephanie Brown is not the company darling that DC is desperate to put over like Jaime Reyes is, so she didn't get the chance to drop all the way down to the basement like that, much less get another ongoing series regardless.
Stephanie didn't have the benefit of being launched during "The New 52!", in which every single title -- including the venerable Action Comics and Detective Comics -- was rebooted back to issue 1, with a massive, media-spanning advertising campaign backing it up. As those books you mentioned show, anything will sell well at first, given that enormous a push.
And given your argument here, they knew how many people would buy a Jaime Reyes series from the last sales number of his first series: 10,000. Notice how that didn't stop them from trying again, anyway...
Again, Steph won't have the once-in-a-lifetime chance to launch as part of a company-wide reboot back to issue 1, with a massive, media-spanning advertising campaign backing her up. The comparison is hardly fair or balanced.
Also, let's see how long Jaime Reyes's second series lasts, statistically speaking...
So, when does the aforementioned editorial favorite, Nu Beetle, get his "toxic" label, then?? This is his second "rodeo", and he's been roped and branded even more quickly than last time. I'm absolutely sure he'll NEVER get that label.
There is a blatant bias at DC, make no mistake about it.
Jaime Reyes is the Hispanic version of Peter Parker over DC.