I would be reluctant to be giving mineral oil at all. It's not a recommended treatment for blockages in most cases, as it coats the blockage so that it can't absorb water to help break it up. But if your bun is still pooping she doesn't have a blockage yet anyways, and just has a gut slowdown at this point. That is what the hay and veggies is meant to help with. The hay and veggies help provide needed moisture and fiber to help keep the gut contents moist and from getting dry, and hopefully prevent a blockage from occurring. The fiber also help get the gut moving and pushing the contents through better. So moisture from veggies and water, and fiber from hay and the veggies, are all essential. It would be a good idea to avoid any cruciferous veggies though, including the leafy ones, in case they are possibly causing any gas problems for your rabbit. I usually stick with basic leafy greens like green leaf or romaine lettuce, cilantro, and parsley. Also are there any new foods or veggies that you recently started right before this happened?