This usage of meal is very unclear. I find it virtually meaningless.
In general, meal has a very flexible meaning. If I say, "I prepared a meal," without further context there's no way to know if I cooked for one person, or for twenty people. This is because a meal is generally the food that is served to whoever, or however many people are eating at that meal.
There are some contexts where meal has a more fixed meaning, such as a prepackaged meal, or one with fixed portions. That is, if I were preparing airline meals (if they still existed), or school lunches, I could say, "I prepared 100 (airline) meals" and it would be clear that I meant I prepared 100 little trays of food and not I prepared food for all the people in 100 different airplanes. In the context of an in-flight meal, we sort of imagine every person eating their own meal, rather than all the passengers sharing one meal.
The problem with this context is that it's a very unusual situation. The intention of the cook was to prepare food continuously for 100 hours; the fact that people were being fed was an afterthought*.
Meal typically means the amount of food needed to feed all the people sharing the meal, but Bassey was not cooking for people - not directly. She wasn't intending to feed anyone, she was only intending to cook a large amount of food. So it doesn't really make sense to describe the food she made as meals.
The writers of those articles likely used the phrase "100 meals" because it sounded like a lot of food, and they liked the reflection of 100 hours and 100 meals.
Note that other sources describe Bassey's output as "almost 100 pots of food" (CNN) or "over 100 pots of food"(Guinness World Records). That's barely more helpful, since a pot of food could be any size. "According to Hilda, each pot of food she cooked was big enough to serve 30-35 people" (Guinness World Records).
So, in the context of the actual event, "100 meals" might mean *food for 100 groups of 30-35 people". But if so, there are surely better ways to express this.
*Apparently, the Guinness World Record rules demand that all the food that's prepared must be consumed, but they don't seem to require anything about where, when, or by whom the food is consumed (Guinness World Records).