* She's trying to maintain a facade: Blanche has always relied on her charm and appearance to get by, and she's desperate to hold onto her fading youth and glamour. She knows she's no longer the young beauty she once was, and she's terrified of facing reality. Therefore, she exaggerates her experiences, lies about her past, and attempts to seduce Mitch to recapture a sense of desirability and control.
* She's coping with trauma: Blanche is clearly deeply affected by the loss of Belle Reve, her family home, and the events that led to her exile. She's also haunted by her past mistakes and the death of her husband. This trauma manifests in her increasingly erratic behavior, and she uses fantasies and lies to escape the painful reality of her situation.
* She's trying to create a connection: Blanche is lonely and desperately wants a connection with someone. She sees in Mitch a potential for companionship and even love. However, she also senses his working-class background and feels threatened by his lack of sophistication. Her attempts to impress him with her "refined" persona are a way to bridge the gap between them and convince him she's worthy of his affection.
It's important to remember that Blanche's portrayal of reality is unreliable. While she may believe her own fabrications, her desperate need to present a false image ultimately leads to her downfall. She pushes Mitch away with her lies and deceit, leaving him with a disillusioned and negative view of her.
The unreal impression Blanche creates ultimately contributes to her tragic fate. Her inability to face reality, coupled with her desperate attempts to maintain a facade, ultimately lead to her being exposed, rejected, and ultimately hospitalized.