We always feed pigs hay so they can munch if they are hungry. For our piglets we leave a pan of pig & sow out for them 24/7 in a creep feeder area. I have never really seen momma pigs sharing from a pan with their piglets, the closest would be letting them root around outside with her.
i would say she for sure looks skinny, pigs during lactation are almost impossible to put weight on once it is lost because their body demands so much to make milk. From what i gather that Mazuri pig feed is only suppose to be 50-60% of their daily intake of feed. The other 40-50% of her feed should be hay, grass,forage,fruits,veggies, table scraps, milk, eggs, basically anything but meat/bones.
So for example if she weighs 50lbs she would need 0.75-1.5lbs of Mazuri per day plus 0.75-1.5lbs of other food stuff. 0.75-1.5lbs is roughly 1 1/2C to 2 3/4C so total per day she should get 3 - 5 1/2C if she weighed 50lbs.
If you have a tape measure you can figure out her weight the problem atm is she is skinny firstly so her weight to feed will be off and she is lactating so weight gain is gonna be hard. I would definitely figure up weight then figure out her feed amount per day and feed her that plus slightly more.
Forgot to mention you can also free choice feed pigs....with her being skinny and the piglets being there and needing to get used to food you can free choice feed but definitely add hay or some other reasonable amount of forage for them to the diet.