First thing first, I'm presuming this is supplementary feeding & she's getting free choice hay/grazing too? If not, I'd definitely be feeding her that. Horses need tiny amounts of roughage going through their system near constantly, so free choice or little & often fibrous feeds are very important.
I would personally not be feeding the 'everyday cubes'(are they cubes or small pellets?) as a main feed, but I would choose something low starch/grain & wheat free, and if it's more than for a treat/supplement carrier, I would consider non-pelleted a better option. Especially if feeding starchy ingredients, I'd be feeding it over at least a couple more meals daily. Little & often is always best, but esp important to reduce potential probs from those type feeds.
Do you mean 'Alfa chaff'? If so, is it straight alfalfa/lucerne chaff? This can be a great ingredient for added energy & nutrients, but I wouldn't feed the sweetened variety and I would feed it as around 1/4 of the daily ration. It is high in a number of nutrients that can be problematic if fed in excess/out of balance.
Oil shouldn't be fed in large amounts - up to half a cup seems generally OK - and horse's guts don't have the enzymes to digest fats in this way, so it is extra important to build up to the full measure very gradually, say over a couple of weeks, and feed it little & often, so the gut can develop & keep alive those necessary enzymes. I would choose a good quality nutritional supp that balances whatever else the horse is getting in it's diet. Services such as feedxl.com are great for help on that front.