It seems like the mental part of her game should maybe focus on not looking too far ahead of herself and staying in the moment. She has great composure, which likely helps with that as she doesn't seem to dwell on missed shots. But I see where often, when she has a clear opportunity to smash an overhead, etc. and has her opponent on the ropes she seemingly gets excited and it's too much/out. Like perhaps she is ahead of herself and has already won the shot without playing the shot. (Sure, like momentum and adrenalin don't factor in, right?). Anyhow, a few shots where she had it she failed to convert and, while that's just part of being human and any athlete will have those moments, some of it likely can be worked on to improve even more.
Easy for me to say, sitting back as an armchair totally unqualified tennis coach. But it's an observation - when she has a chance at a clear winner or even opportunity to take charge, sometimes those get away from her. She'll be fine/awesome...experience is huge and she is showing some true champion form and composure...I don't like some of the attitude some others display. Sure, they're competitive and fired up but it gets to be overkill as they constantly sneer, shout and challenge shots and rulings.