She will have received a warning or enquiring letter first. My partner is a lorry driver and can be away up to 12 weeks at a time. I was claiming tax credits when we first started seeing each other. He had his own home, but never really stayed there - he would stay here when he was back, I’d do his washing, we would have food together etc. We hadn’t been on holiday together, but had been on a few weekend trips when my mum was willing to have the kids. For context, I would receive £370 per month for help with nursery fees and then I’d receive the single person council tax.
I was (wrongly) under the impression that if they didn’t spend more than X nights per week at your house, you didn’t need to declare it. But, I received a letter in the post stating that they believed I was in a relationship. They gave examples as what could be perceived as a relationship, such as positing on social media together (which we did), going on holidays together (not quite holidays, but still), and if someone were to ask what we were to one another, would they say we were in a relationship. I felt this answer was “yes”. It said on the letter that if any of these instances were a correct example of my life, I needed to ring them and stop receiving tax credits. I did so immediately, told them how long we had been dating, and that was the end of that. So, it’s likely she’s received something similar and either ignored it or said none of it was correct.
It’s a crap system as my partner wasn’t my children’s dad. He didn’t have to contribute to my household. But as a result of us being “perceived to be a couple”, I had to ask my partner to cover my losses as I simply couldn’t afford it. Eventually he put his house up for rent and moved in - still here today and we now share bills but for over 12 month I was lucky that he could cover that shortfall for me.
Whilst I do believe you shouldn’t be claiming if you’re not single, women do have the right to date and begin relationships without that then meaning that all benefits stop. I was lucky that my partner was able to contribute, but in reality he didn’t have to - they weren’t his kids and this wasn’t his house.