just describe a girl

If you need any (non-countable nouns) advice or support, you can always go to (or "turn to," "rely on" or "count on") refer to Jackie, she’ll listen and help. She believes that everything in our lives is not accidental (or "She believes that nothing in our lives is accidental"), and (that) sometimes a complete stranger can lend a helping hand. Jackie is self-critical (Hmm... this is correct English, but I'm not sure exactly what you mean here. Maybe "self-aware" or introspective or something. She likes books and can spend hours wandering in (or "wandering around in" or "browsing in") bookstores.

Your English is very good -- I didn't really find many "errors", rather, I made a few suggestions for fine-tuning your writing.