The rule is you can go from hydro to soil, but not soil to hydro.
The root cortex grows differently in soil compared to hydro.
That's why your plant gets stressed going from soil to hydro. going from dry--> to wet. it's not set-up for it.
You might be ok with a 3wk. old plant. The root system is relatively young. You might want to cut some of your root system off, and be prepared for plant stress. Maybe use some super thrive to help with plant stress until she gets acclimated to the water.