I believe it's very possible that she may have encouraged him. And to be perfectly honest they had been in league. Although of course Bamber would be the spearhead and carry it out.
I think post massacre the conscience may have come out to play. A possible percentage wise for the sorrow for the victims but more likely for self preservation. She may have been genuinely scared that if Bamber came a cropper he would confess and implicate her.
She's in a decent position either way if her and Bamber were in league together. He will never confess and highlight her involvement as it would scupper the most desired goal of his. Namely freedom.
I believe her WS. Which was completed the day after she approached the police.
It is up to the reader to decide if that was encouragement.
Don't believe she would encourage the murder of men, women & children.
Doubt that a 20 year olds main interest was money. If it was she would take up June's offer of a house.
Dismissing his 'tonight's the night' call would have encouraged him.