What a lovely idea!
For me, I felt the best between about 16wks-30wks. Before that I was sooo tired and has m/s. After it, I was again really tired and with your belly getting a fair bit bigger then,things are getting hard physically. This pg has been hard though because I have had issues with my back and pelvis so if she has any issues like that, I would ask her what she thinks. It can be a really personal thing. Everyone is different in pg!