You've written the thoughts themselves very well. When I read those, I feel as if I'm in her head.
What pops me out of the viewpoint are the places where you tell us that she's thinking:
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Her mind immediately flooded with panicked thoughts.
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She realized...
These are not her thoughts in the moment. They are some narrator's commentary on what's happening in her head. And that is where the viewpoint shifts occur.
If you get us into the character's head, you don't ever need to say "she thought" or "she realized." That sort of commentary is unnecessary because every word of the story comes to us through her perspective. Every sensory detail comes through her senses. Every bit of reaction and opinion and thought is her reaction and opinion and thought. We know this because you've drawn us into her head.
You're doing fine with her thoughts. Drop the parts where you tell us explicitly that she's thinking.
Edited to add this example:
Mandy arrived at 3:00pm, but he was nowhere to be seen.
Where was he? Was making the request via email inappropriate? Oh, God, had he gone back to California already?
No. That was silly. She was simply being neurotic.
She took in a few deep breaths and felt her heartbeat slow.
(I'm not happy with my transition between the first and second paragraphs. But I hope you get the idea. No need to say she's thinking. Just write her thoughts.)