This is a variant on the stone-throwing answer.

Have heavy draft horses available in your world. Fit one out with a reduced size version of a jousting saddle, with back support for the rider. Her legs won't reach round to the horses sides, but that does not matter because it can be led.

Sitting on the horse will give her a better, safer view of the battlefield, looking over the heads of her bodyguard rather than having to stand in front of them. The horse will absorb the backwards thrust when she throws. It can carry a lot of ammunition. When she needs to rest she will already be in an armchair.

This is a variant on the stone-throwing answer.

Have heavy draft horses available in your world. Fit one out with a reduced size version of a jousting saddle, with back support for the rider. Her legs won't reach round to the horse's sides, but that does not matter because it can be led.

Sitting on the horse will give her a better, safer view of the battlefield, looking over the heads of her bodyguard rather than having to stand in front of them. The horse will absorb the backwards thrust when she throws. It can carry a lot of ammunition. When she needs to rest she will already be in an armchair.