Signing with WME is an a big deal. I can't really think of any other female track and field athlete that has a bigger contract than Sydney right now or in the past. WME can see the marketing potential of Sydney McLaughlin beyond track and field and they have positioned her perfectly. I'm betting that she was advised to skip USA outdoors just to minimize injury risk and generate more hype and interest during contract negotiations. So far her management has been genius.
I agree with Douglas_Burke, her talent level is exceptional. With the good coaching and discipline, world records and gold medals are eminent.
However, the enormous contract money and the WME connection is actually what makes things dicey. WME has a lot of celebrity connections and I suspect that if she relocates to train with a coach in California that the lure of celebrity and parties may be too much to resist for a 19yr old. WME will have her on tons of magazine covers before you even know it.
All that being said, if the ultimate objective is money, her performance doesn't really matter. She'll make the more money on the circuit as the Anna Kournikova of Track and Field than anyone else. Kournikova was never ranked higher than #8 in the world and never made it past the semi-finals of a grandslam tournament.