Hello
@NK99 Welcome to the forum
Sorry to hear of your partner's situation with not taking insulin.
@catapillar has explained this very clearly, it is a condition that is recognised albeit only more recently, that this is a type of eating disorder, the danger is that without her insulin she will require urgent medical assistance.
She needs to seek advice as quickly as possible, so speaking to her diabetic team, GP or contact 111 as soon as possible.
Please urge her or do this for her as soon as possible and let us know how you get on ? We cannot do any more other than tell you what the consequences will be unless she does this, however we are here to support you, best wishes J