That plant looks a bit starved for light. There's a fair bit of stretch going on, though I've never grown the WW myself so perhaps that is just the normal characteristic of that plant.

3 weeks is going to be pushing it. By the looks of it you likely need at least another 4 - 5 weeks plus a few days of total darkness. Be patient. The plant can gain 30% weight in the last few weeks. If needed, you can leave her by herself for a week. Just give her a thorough watering / flush before you go.