That is amazing and you should just keep talking to them, even if you feel you cannot receive their response. They are truly amazing beings.

I am curious, how did you come to the link between Sif and Mother Earth that should make them the same?

Have you asked your spirit guide how to further develop your abilities to receive messages from spirits. For me it is just a natural thing in my every day. I do not spend time meditating and so... I just speak with my guides (in my head) as I would anyone else. Though if I am alone in a room I will get no response