hi N.,
sometimes there is an anxiety of seperation that hits children at diff. times. she just needs to know that you are near with her beckoning call.
I would suggest that you pray peace over her at night and a peaceful sleep in Jesus' name. Also is there anything new that has been given to her as a gift that could be scaring her? is she eating or getting some sugar before bed which could be stopping her from having a restful sleep? is there a new noise in your house that may be scaring her too like a new appliance kicking in?
Just some thoughts but hope they help. Just tell her how much you love her and then cover her and back to sleep. when it continues jsut walk in, say nothing and put her back to sleep. keep doing this without speaking to her. it will get less and less each night....
blessings, L.