About Dumbledore 's absolute trust in Severus . And then Tonks lied . She pretended that she herself did n't know the reason why Dumbledore trusted Severus . ' But Dumbledore swore he was on our side ! ' said Tonks urgently , trying to convince herself more than anything .

Question: Why did Tonk lie to herself about Severus ?
Answer: Tonks lied to herself because she wanted to be convinced .Tonk lied to herself because she wanted to believed in Dumbledore .Tonks lied to herself because she wanted Severus to be trustworthy .Tonks lied to herself because Dumbledore would have wanted her to .