Hi
Has she had any bad experiences recently regarding doors and windows? Collies often generalise bad experiences to odd situations and she may have been frightened by a noise or similar and now believes that open doors and windows are the cause.
She is also getting older and may be experiencing cognitive problems due to old age and you may have to visit your vet to have this checked out.
Don’t make a big deal out of this in front of her and reward her well for coming in. If she feels that you are anxious she might not understand that it is her behaviour that is the cause of your anxiety and just feel that not only does she feel bad in this situation but you do as well.
When she is inside you can begin by opening windows very slowly a tiny bit at a time and gradually over days and weeks extend the amount and how open the windows are. At the same time play a fun game or give her a nice treat to help change her mind about windows and doors. Do not try and coax her in or make a big issue about it and tell her all is well by remaining clam and relaxed.
If after a few weeks she is still having trouble arrange to seek help from your vet and they might be able to refer you to a qualified dog behaviourist.
Hope this helps
Rosie Barclay.