Scratching is a natural behavior for cats. Here is a link which may be helpful:
https://www.petcoach.co/article/5-ways-to-deal-with-your-cat-s-scratching/Eating foreign objects can pose a significant health risk. This can be very bad as strings and other foreign objects can cause blockages, lacerations or perforations within the intestines which can be life threatening. This may be a difficult situation to correct.
Some cats may respond to environmental enrichment and finding energy outlets. Toys can come in many forms and some are even interactive.
https://www.petcoach.co/article/common-home-items-that-make-great-cat-toys/Also, providing other environmental enrichment can help. Here is a great article about cat's instinctual needs:
https://www.petcoach.co/article/why-every-cat-needs-a-place-to-climb/Using a Feliway diffuser and setting aside 30 minutes a day for vigorous play for your cat can also help. Lastly, you may need to safety confine Maisy so she cannot eat things she should. Make her a room that has been cat proofed where you put Maisy any time you cannot directly supervise her so that she is safe. I hope this helps.