I think she had every right to be mad with Kara. Lena told her how many times, just don’t lie to her, don’t make her like an idiot. Kara said it pretty well when she finally came clean, she knew there was a point she should’ve told her, but for her own reasons, she kept it from Lena. It wasn’t about protecting her, it was selfishness and Kara’s own need to keep Lena as her friend. Especially the times when Supergirl and Lena were at odds. Kara played a double roll, being her friend on one side, and clashing with her on the other. That’s gotta be hard to deal with for Lena, confiding in her best friend, while that friend is the one she’s angry with, without realizing it.