Porridge and a teacake isn't much really and on it's own says nothing about what she eats later in the day. I prefer to eat earlier in the day, rather than the evening because that is when I am hungry.
I would go for a higher protein breakfast than porridge and a teacake, because even porridge makes me more hungry rather than all that 'keeps me going until lunch' bollocks.
Calorie wise, my ideal breakfast would be around 7/800, then 4/500 for lunch and starter sized 2/300 calorie evening meal as that is all I need.
Any less in the daytime and I am constantly starving but if I get to eat more earlier in the day I tend to eat better and eat less overall.
A few years ago I was working away where I spent an extended period eating all three meals a day with several colleagues and it was blindingly obvious why the slim people were slim and the overweight people were overweight. I am a tall sized 12 so slimmer than average in a lot of circles.
Overweight colleague 1 had a big bag of haribo and lots of fizzy drink every day and always 2 or 3 courses at dinner.
Overweight colleague 2 was constantly buying cakes and biscuits for everyone as an excuse to tuck in herself.
Most people had 2 or 3 courses at dinner whereas I just had a main and saved half of it for lunch the next day where practical or got something like soup/roll or a ready meal for lunch, whereas most others got a big pile of rubbish from Greggs or McDonalds.
But all they ever noticed was that I had 2 or 3 times more breakfast than anyone else
. So they would have a bit of cereal and some toast and I always had eggs, bacon, mushrooms, tomatoes etc.
I am firmly of the belief that it is portion size, sugar consumption and drunk calories (fizzy drinks, alcohol, smoothies, flavoured coffees etc) that separates slim and more overweight people in almost all cases.
I almost never drink anything except water, coffee or tea with just milk, or moderate amounts of alcohol. Eating more plus extra calories to drink could easily add an extra 500/1000 calories a day, which over time adds up to a lot of extra weight.