It doesnt matter whether hubby confirms it or not. If it didnt happen like that - but both say it did - it is still perjury.
My reading of this situation is that Seeker and her husband had an altercation during which he decided to call the police. She went to grab the phone off him and it is thought at this point caught his face. To some extent, it is irrelevant whether she caused an injury or not at this time - the mere act of grabbing the phone is an assault. Indeed, there doesnt even have to be contact to constitute an assault (definitions here
http://www.cps.gov.uk/legal/l_to_o/offences_against_the_person/ - note the difference between an assault and a battery).
Presumably she was then interviewed under caution and, as a result, offered a caution. I have no idea what she said in the IUC, but this will be admissible in Court. It's going to sound pretty odd if in the IUC she says "yes I went to grab the phone and must have caught his face with my nail" and then in COurt says "he cut himself shaving".
A canny prosecutor will charge this as an assault simpliciter.