Hello My new born is transitioning into a cot soon and in regards to bedding, is it okay for her to have a few layers on her matress like, mattress protector, fitted sheet, mattress protector then another fitted sheet to speed up the cleaning sheet process for spit ups during sleep? She will be in a safe sleeping bag. If this practice is not safe bedding, can I place a washer tucked in near her head? She is 8 weeks old, not rolling yet

It is important to ensure the mattress is firm & remains firm when waterproof mattress protector is used. Adding an extra mattress protector, may reduce the firmness of the mattress.
….always make sure that the waterproof mattress protector is strong and a tight fit. Never put soft bedding under the bottom sheet, such as a sheepskin, as this makes the sleeping surface too soft.
https://rednose.org.au/article/what-is-a-safe-mattress

Even tho’ your baby is not rolling yet, there is a risk of head/face being covered if the washer was to become loose as baby wriggled & moved during sleep.