I would probably use at least Liu Jun Zi Tang to bolster the Spleen, provide some energy and warmth, and drain some Damp. Kan makes that in liquid form (Six Gentlepets). You would then take about a ml of the tincture, combine it with about 50 ml of spring or distilled water, then succuss it 200 times or so against something resilient. We combine everything in a glass dropper bottle, cap it, then bounce it off a thick soft cover catalog or phone book 200 times until it looks very frothy. Thereafter, the owner should succuss it 10 or 20 times against the palm of his/her hand before drawing up the dose, which should be substantial, say 1/2 to 1 ml, given a few times a day. It should be kept in the fridge.
A better formula for this cat is probably Zhen Wu Tang, used to manage CHF. It is a stronger Yang tonic, moves Blood (which appears important in managing chylothorax) and drains Damp. You may only find it in powder form. If you do, you can still make a homeopathic. Just succuss maybe 1/2 to 1 tsp of herbs in about 50 ml of water. It will taste stronger but probably still be manageable.
If the chyle becomes Blood tinged, consider Xue Fu Zhu Yu Tang. If the cat warms up and becomes stronger, use it in tandem with whichever of the above you're using.
Hope this helps!
Steve