Other than perhaps Mo and Galen, is there anyone more worthy of doping suspicion than Shannon (other than perhaps Trenier a few year back). Her late career trajectory is incredible and worthy of scrutiny. My guess is Jenny's tone is informed by concern/assumption/knowledge that Shannon is doping to beat her.
Have you looked at Rowbury's record? It is so much like Simpson's that if Rowbury is suspicious, then so is Simpson. (This has been pointed out several times here since Monaco. If you look, I'm sure you'll find the posts making this point.)
If you look at their pbs, they have pretty much the same times, except at the 5,000. Since Rowbury ran the 5,000 seriously a few years ago, that's no surprise.
A lot has been made of Rowbury suddenly running a bunch of pbs after going to NOP. That certainly sounds suspicious. However, if you look, you see that she didn't improve by that much. For example, in the 1500, she'd run 4:00 low several years ago. So until this weekend, her pb hadn't dropped that much.
Simpson has the same sort of progression. She ran a fast 1500 at Pre while still in college, and then slowed way down. Then suddenly, boom, she's consistently under 4:00.
FWIW, the USADA agrees with you. A quick peak at their records shows that Rowbury's been tested way more often than Simpson. Simpson has basically gotten a pass.
My view is simple. Given how fast they run, I wonder about both of them.