The thing which Jessica needs to complete before she can send her message is:
This refers to the the transformation of a receipt of a sensory signal and saving it in the long term memory which helps in memory retention and subsequent retrieval.
With this in mind, we can see that because Jessica's best friend forgot her birthday and she is disappointed and ius struggling with words to convey her feelings, then she has to first complete encoding.
Read more about encoding here:
https://brainly.com/question/24881756