Early on a Tuesday morning last month, Marcello and her husband Robert began their journey home to Maryland in the US with their children, expecting a long but straightforward trip, she told The Local.
But as the family were travelling to the airport on the S-Bahn, they encountered a plainclothes ticket inspector who informed them that the tickets they had bought weren't for the right zone and that they needed to pay €120 in fines on the spot.
As tourists to Germany, Stephanie and her husband were unsure whether the inspector was a real Deutsche Bahn (DB) employee, but apologised for their mistake and asked whether it would be possible to pay for the correct tickets instead.
According to her account, the DB inspector refused, and demanded that they withdraw the money from an ATM at the airport to pay the fine in cash, to which they agreed, though still doubtful of the legitimacy of the situation.
Despite their compliance, the lone ticket inspector was joined by another inspector shortly after. Both DB employees remained with them for the entirety of the incident, hovering over the family constantly.
"We were with our kids, did the agent seriously think that (Robert) was going to bolt and make a run for it?" asks lawyer Stephanie.
Robert, a federal law enforcement officer, asked to speak to the ticket inspector's supervisor, but the response he received was "he is home sleeping".
Once the family arrived at the airport they withdrew cash to pay the fine, but by this point, four more inspectors had arrived on the scene, in what Stephanie calls "an obvious intimidation tactic".
"It felt like we were being robbed and then treated like criminals, all in the presence of our children," she said.
Given that there were now six officers to deal with one fine, Robert requested to get the police involved.
According to Mr Marcello, when the police approached to deal with the issue, one of the DB inspectors ran up to the officers before the family had a chance to explain what had happened, despite the fact that the Marcellos were the ones who had made the complaint.
The police officers confirmed that the six inspectors were all DB employees and that the fine was correct, so the family handed over the €120.
But once the Marcellos had paid, the DB employees filed a complaint against them with the police, upset that their legitimacy had been questioned and claiming the family had said that the inspectors weren't German.
After lots of discussion in German which Stephanie and Robert couldn't understand a word of, police officers took a photo of Robert's passport to fill out a report.
'Needless to say we will not be coming back'
Stephanie, Robert and their two children then boarded their plane to Washington DC but have been put off by the ordeal.
"Needless to say we will not be coming back," says Stephanie, "We will not recommend [Germany] to family and friends either."
Mrs Marcello thinks the whole thing is a shame for Germany, as whatever revenue is generated from fines is small compared to the money that won't be spent by tourists put off by their bad experiences.
She says she has tried to contact DB several times about the incident but has simply been told that the case is "being processed" and asked for her patience.
She doubts that DB will even receive the money she and her husband paid.
A Deutsche Bahn spokesperson told The Local that “normally our employees give passengers who travel without tickets a demand of payment which must be met within a 14-day period. Payment of an increased demand for compensation in cash is only demanded in exceptional circumstances.”
This is far from the first time conductors have demanded passports and cash payments from foreigners. Last year the Local reported on two other incidents in the Munich area alone, when tourists were targeted by inspectors.