she can call and apply as "seperated under one roof" - she will have to provide additional statements in regards to her circumstances. given you know what is happening she may as you to provide a written statement that you know they're seperated and all that stuff...

definitely better to call - going in to the office, she will be sent to a phone to call the call centre. the call centres have more appropriate staffing levels to help in these circumstances - the offices now only deal with finalising and granting payments, receiving forms etc