Burying the money envelope

I think she thought it would be a better hiding place than her apartment in the short term. Her neighborhood had drug delaers knocking on the door trying to sell drugs to Claudy. Druggies will kick your door down to get anything they can sell for a fix.

Yeah she wanted a safer hiding place for the money which she later decided she would use for a good cause following his demise (the setting up of the bank account in the child's name).

Follow the money... its no accident the movie starts in a bank.

. After Claudy convinced Lorna to look after his money, she looked after him.

. After Claudy died, she buried his money.

. When the phantom gestation begins, she tries to bank his money to grow its inheritance.

At the end Lorna is just left with the guilt money that Fabio offered in compensation for deceiving her.