Well, for a start, nobody apart from the visa officials and Gamu's mother are aware of what she did/didn't claim and what she was/wasn't entitled to.
Immigration laws are a pain in the arse and constantly change. My ex has been through years of dealing with the home office. He's a US citizen, and has really struggled with them.
Here are just a few snippets from the fabulous time he's had with them. They rejected his visa application, saying that he had not supplied all the appropriate documents. He then got them to send a copy of every document they had to his lawyer. His lawyer then went through the bundle with them on a call and asked exactly what documents were missing - none were actually missing. They just weren't looking properly. The Home Office then lost his passport for six months. Then, they refused again, so it went to trial in Glasgow. The judge presiding was on secondment from California (not exactly clear why - I didn't know they had such things but anyway) - fortunately. The hearing was about whether or not ex, who has been resident in the UK for about 10 years, settled, with friends and family here - his whole life could stay. No one from the Home Office even bothered to turn up to the hearing. Unsurprisingly, the judge decided in ex's favour.
So, a lot of mistakes are made by the Home Office and immigration, and individuals. When I was advising on immigration issues as a student (pro bono place), it was incredibly difficult, as the requirements do literally change week to week.
And as for whether or not her family are safe: if you have any connection to the UK you're viewed as an enemy by ZANU PF, and even though it no longer makes it to the news in the UK, crazy stuff is still going on. People being beaten up, thrown out of their homes, raped. It could happen to Gamu and her family.