People have laid out the moral considerations pretty well, so let’s look at a different angle. A little thing they taught me once in a negotiations course was value building vs value claiming. They didn’t need much morality to arrive at the idea that some situations aren’t win-lose, but in some situations it’s possible that someone will benefit a lot from something that doesn’t cost us
that much to give. The last part sounds wrong, but if we peel the capitalist thing away, sometimes we can use creativity to come up with a solution that doesn’t consume too many resources - or too many resources we’re short of. If you can get better deals on food than the maid can, that’s great. If you can pick the food more wisely than she can, that’s great. And so on. You can also have her eat with you, which will both save money (it’s nearly always cheaper to cook for more people than for less) and give her a greater sense of belonging. You can rationalise her tasks so that say, you aren’t calling her downstairs so she would hand you the TV remote while she’s taking a nap or otherwise resting (not saying you’d do that)… Or she doesn’t have to go somewhere again because you forgot to tell her everything the first time (again, not saying).
You might want to look into the reasons why she spent money on things other than food and then ate the food that was meant for your children. It’s possible that she had a family to feed and it’s possible that she bought things she didn’t really need because she thought she could eat food that wasn’t meant for her. In the first case, you may want to give her a rise if you can afford it. In the second case, perhaps an educational conversation would be in order (it’s not a 20 year old from a develop world and half way through Bachelor’s degree).
As far as the choice of food goes, I suppose you, or strictly speaking your wife, was acting in the maid’s interest and wanting good for her (you mentioned healthy food). That’s good, but if, say, you’re American or European and she’s local, she can have a different metabolism and different needs of particular food ingredients - plus, sometimes there may be a good reason behind traditional local choices of food, while what we think about this or that kind of food being healthy or healthier than something else isn’t always true. Plus, I’d try to avoid expecting her to conform to my ideas of how one should live (e.g. is it because it’s good for her or is it because I want her to be the way I want her to be?).
You aren’t morally wrong in providing her good and sufficient food if the agreement was food but you had been providing money for food instead (regardless - it can be seen as a pay cut). But you might as well explain to her why it’s important to eat healthy and that you care about her (which you do). At the same time, the maid isn’t morally wrong in using electricity (and frankly, she should be allowed to - why bother having her eat fruit if she can’t have a warm meal?). Also, why buy separate food for her, well, as long as you don’t eat European while she eats local? You could probably save money having her eat with you. Probably could take her shopping with you and explain a couple of things while at it, as in being a good example of how to spend money judiciously. And she needs a day off. It’s natural law that there needs to be a day set aside for rest. It doesn’t have to be a Sunday for a non-Catholic, it can be a different day. Still, she shouldn’t really be expected to work hard and run around on errands while (and if) you’re resting and celebrating. You can work out some solution there, but you can’t have her work without a day off a week. And make sure she can practice her religion, that is pray when needed to, go to the mosque when needed to, have a day off when needed to and so on. The way I see it, not havy any day off (well, obviously,
some things need to be done on Sunday, but that’s not e.g. a complete vacuuming of the house plus cleaning the floors plus mowing the lawn etc.) is a much bigger issue than the $2 on electricity and possibly bigger than taking the food that wasn’t meant for her (as long as your children didn’t go hungry as a result).
One final thought, if she really has some family to feed (which is possible, but certainly not sure), maybe it would be possible to find a job for those who can work (moving packs around for cents is still better than looking for cans in trash to sell for cents)? Or, if she’s already sharing the pay with maybe she could share the work too, e.g. with a sister? It’s pretty much the puzzle work at this stage: trying to find a creative way to make things better for everyone. You
could allow her to have some (name removed by moderator)ut or reward her to some extent (financiall or otherwise) if she shows she can spend reasonably (presuming you don’t know that she spent the money on trivial things) or perhaps you could give her some more money if she has a difficult family situation.

Maybe there are more things you could do for her, say, giving her access to something she doesn’t have but doesn’t need to own either, teaching her how to do some things better… anything that’s more available than money itself.