Answer:
Fake image, representation, a foil.
Step-by-step explanation:
An illusion is a projected image of what or how something appears to be, which is not the real case. It presents an unrealistic foil for concealing or hiding behind a mask or covering, and gave a much more 'socially acceptable' appearance. It is meant to present an image which is deceptive and meant to misled people in believing it is the truth.
In the sentence, "Jessica's designer clothes and high-end jewelry" presents an image of who she appears to be on the outside, pretending like she's rich and wealthy. But the reality is that her 'wealth' is just an illusion for the 'poverty' she is in, having "little money and often struggling to pay all her bills".
Thus, illusion in regards to the sentence will be "a fake image, a representation" of what she wants to be but not what she really is.