Why do you think Aunt Jennifer created animals that are so different from her own character? What might the poet be suggesting , through this difference?

Aunt Jennifer's tigers symbolise her spirit of freedom which is subdued within her. She creates them as she cannot express herself freely in the male dominated society and feels oppressed under it. Her tigers are strong, chivalric, and fearless and stand in strong contrast with her own weak, and terrified persona. 
The poet suggests through this difference the polarisation of the genders. The women, as symbolised by Aunt Jennifer, are mentally and physically suppressed in a society where men are given the upper hand.