Could a girl be considered to have left Islam due to her questions regarding creed and faith?

These whisperings do not harm your faith as long as you detest them, and you will be rewarded for your struggle to get rid of them. Do not pay attention to them. Whenever they come to you, seek refuge in Allah and stop them. Learn religious knowledge, and read books on the topic of Divine Decree, such as the treatise by Sheikh Ibn Uthaymeen or Al-Ashqar's book "Al-Qadar (definition)" (Divine Decree), so that your confusions may be removed. Seek Allah's help against distraction through supplication, strive hard in acts of worship, and keep company with righteous people.