If devika has asked arjun to give his blood and not asking his type. Arjun is going to start thinking how she knows so much about him. I think arjun may get suspicious about her. If devika ever sings that Krishna song to her son than arjun will really know that she is bhoomi.
Also with them living together in the same house, i don't think that they will be able to stop their attraction towards each other no matter how much devika tries to deny it. It would be good to see some romance between them and it would be fun to see shefali go green with envy