。
She was so embarrassed her face turned bright red.
Literal
She [topic-は] embarrassed-and face [subject-が] bright-red became.
The causal te-form on i-adjectives is built by replacing ~い with ~くて: はずかしい → はずかしくて, meaning 'because (she) was embarrassed.' This is the most common way to link a feeling to its physical effect. 真っ赤 takes the prefix 真っ ('truly, genuinely'), which intensifies colour adjectives — 真っ白 (pure white), 真っ青 (deep blue, also describing pallor), 真っ黒 (pitch black). The construction X が ~になる ('X becomes ~') puts the changing entity (顔, the face) in the subject slot under the topic-marked person.