It is very hard to advise on this without understanding the cultural norms of you and the family. How does Rekha's husband fit into this picture? Would he be interested in a type of communal living with partner exchanges? Otherwise seems like it would be difficult to have sex with Rekha with everybody living in one place.

Many years ago I tried a "sister swap" (they both had long hair but the "other" sister had big boobs and ass - they were both adopted, not genetically related) it failed miserably and I wound up with no girl. But this was a conservative Pentecostal family, totally different situation.

In any event, sounds like you're living the dream with Maya. Maybe you just need to keep helping her growing her hair even longer.