Choose a command word you are happy with and use it each time you pop your girl in her crate, or she settles on her own
it takes some time but well worth it in a pub when you want some peace
I use "snoozie" which is from the alarm clock in a morning and now very embarrassing but works
If she only does the "shroomy" behaviour when there are lights/shadows she does seem to be a bit OCD - spaniels seem to be a bit prone to it but make fabulous drug/bomb detection dogs as a result given you can train the trait into ball obsession = ball reward for finding X. Your gundog trainer should be able to help you with coping strategies - although you seem to be recognising and dealing with the behaviour at the time
have you taught her the stop whistle? It would be a good opportunity to train and try to break any habit/ritual she is developing.....
If her behaviour is the same, with or without shadows/lights then she may just be very pleased to see you and given her age.......teenage......it may all be perfectly normal as Lorna says - still a good opportunity to practice the stop whistle in this house!
Jayne (pearl age 4.5 scs, coral age 8 months wcs)