1. She has this problem, but she sees it as a temporary situation. "I've been to the library" means she went there, and came back. These are two different pieces of grammar.
2. Really, not much difference when the action follows "start". It's very different with other verbs, such as "try", "stop" and "remember"!
3. Use "because", not "cause". These are two different words. Beware of this learner mistake. I'd use "each of them owned one as well". You need the past tense of "take", and it's easier to write "to go kite-flying" instead of deciding on "it/them"