Oatmeal baths tend to be soothing. And if you follow it with an oil rinse, it would make her feel much better. So an oatmeal bath now, even though she had a bath 2 weeks ago, is not going to harm her. It might actually be better for her, as you are helping to moisturize her skin.
However, if you are really worried about bathing so soon, you can put the flax oil directly onto her back. Also, you can put her in the sink/tub, open a capsule into a small cup, then fill that cup with warm water, then pour that onto her back. I like oil rinses like that better, because I feel that it spreads the oil more evenly across their back, more so than just dropping the oil.
With Myles, it sounds like he has been scratching a lot, to the point where his skin turns pink. You may not see him scratch, but he is obviously scratching. So it sounds like an oatmeal bath with an oil rinse could be good for him as well.