I actually wrote a newspaper article on this last year.
The government release statistics detailing the finances surrounding benefit fraud.
First, the amount of disability benefit fraud is negligible (you don't say what kind of benefit fraud she has reported, but cases like this usually are disability benefit - certainly Mumsnet is very keen on "disabled people committing benefit fraud" threads), yet disability benefit fraud receives an amount of attention that is hugely disproportionate.
The largest percentage of benefits fraud is actually pension fraud (meaning, people of pension age who lie about their personal circumstances to receive more state pension than they are entitled to), but you never hear a word about pensioners defrauding the state, you'd certainly never see a BBC TV show where a TV presenter goes around confronting elderly people who are stealing from the government by fiddling their pensions, even though pension fraud is eight times higher than DSA fraud.
Why? Because pensioners have the highest voter turnout, and no political party wants to risk pissing them off. So pension fraud continues, while disabled people are demonised.
Second, something like 89% of all reports of benefit fraud are found to be fraudulent and/or malicious reports. Ie the person claiming benefits is not committing any fraud, the person who reported them was either deliberately lying out of malice, or ignorantly assumed they weren't entitled to benefits due to stuff like "I saw my neighbour gardening once so they clearly must be pretending to be disabled to scam benefits" without realising the neighbour has a terminal diagnosis.
I don't have the exact stats to hand, but the government spends significantly more money investigating claims of benefit fraud, than they recover from genuine cases of benefit fraud.
People maliciously reporting people they dislike for benefit fraud costs our country millions.
If the government stopped investigating benefit fraud entirely, it would actually save the government money. That would never happen, because benefits claimants are a useful scapegoat who the government and the media have demonised to the point most people are extremely surprised to learn that disability benefit fraud is so extremely low, and that most allegations of benefit fraud are found to be false.