How on earth can she laugh and be so cheerful in jail?
Because she, ICA, has so far been so successful at covering up the murder of her 2 1/2 year old and all the attention is directed to her. She has room and board and isn't moving from place to place looking for a bed and a shower and JB visits her and she is enjoying her celebrity status.
She scams her parents and her brother. She lies 24/7 and she has all the time in jail to pretend and prepare.
She deflects the conversations and says little nice things about the people in front of her to keep them engaged and supportive of her lies. Despicable
Thank God she didn't fool the police.