The lost inheritance
For some reason, Glicera believes that she is entitled to a better inheritance than she receives when her father dies. Like the prodigal son, she wrongly believes that she is entitled to the money, as if she has earned it. This represents her false sense of entitlement and the way she plays the victim when life isn't easy.
Melladore's abandonment
When Melladore promises Glicera love and then abandons her, that represents Glicera's commitment to play the victim about the money, because instead of condemning Melladore for using her, she condemns everyone, because she feels that life is unfair since, if she had been rich like she was "supposed to be", Melladore would have married her. She's still finding ways to feel as victimized as possible.
Grubguard's sin
Grubguard represents something specific in the story about Glicera's character. Through Grubguard's character, we see the cycle of abuse repeat itself. Just as Melladore abused Glicera, now Glicera feels entitled to abuse others in the same way. In the process, Grubguard commits a crime for Glicera, and she keeps the money and runs. This crime symbolizes the shame of Grubguard's own thirst for love, because he was willing to breach his integrity for some young woman's affections.
The humiliation motif
The reader can easily deduce that Glicera has spent her life of privilege and wealth looking down on others for having less than her. Then, when the inheritance leaves her disappointed, she feels humiliated because of her wrongful opinions about money. Then she feels embarrassed, humiliated and used when Melladore uses her for sex, so she absolutely humiliates some other person, in order to punish the universe for her own humiliation. This motif is how this all ties back to Glicera's own desire to be loved and justified, but she's picking a wrong answer to those problems.
The role of Laphelia
Laphelia is a symbol in the story. She is literally a vestige of Glicera's father's money and privilege, because she is the family servant. In this story, she represents the voice of privilege, because she always encourages Glicera in her privileged assumptions. In plain English, she is a yes-man who tells wealthy people what they want to hear. She represents Glicera's tendency to indulge in opinions that shouldn't be indulged.
