started to grow a plant on the window ledge

Right i bought weed about a month ago which had in it a few seeds (althought the weed was fine).

I put one in a smallish pot with some compost and it has grown. Its about three weeks old.
It is in my conservatory which gets the sun all day.
Its already about 20 cm tall and has a few big leaves and smaller ones underneath. The stalk is still verry thin though and it is held up with a small stick.

Will it keep on growing in these conditions? Should I repot it into a bigger container?
Is there a good chance it will be female if the seed come from comercial grade weed?

I would also like to keep it fairly small as its in my mums house!

Im not expecting much, i dont want a massive plant with huge bud for a knock out smoke. I would happy as long as it didnt die. Help appreciated

Cheers.