no, i wouldn't replant if it can wait that long for water. and keeping the smaller plant
with it is good for the health of both in this instance. the problem you have is the overall humidity isn't hight enough. take a shallow tray, put some rocks or pebbles or something for the pot to sit up on, out of the bottom of the tray, the fill the tray with water, just until it doesn't touch the pot.
also, watering once every 3 weeks may not be enough. check the soil to see if it is dry sooner, if so, give it a "small drink" between times.