Hi there
As a vet, I agree that a swelling at the top of the foot could be an abscess (where either damage to the bottom of the hoof and infection has entered, or damage to the skin/hoof wall at the top where infection has got in) or an effusion (a swelling caused by fluid) of the joint. This can also be due to infection entering, or due to something inflammatory (irritating) in the joint such as arthritis or a sprain.
Lancing it would be very bad if it is the joint, as this would leave it open to the atmosphere and potentially further infection. Long lasting antibiotic injection would be the best option for addressing the infection, and the painkiller is likely to have anti-inflammatory effects on the joint and swelling. If she's eating well and moving around reasonably, this is a good sign, lameness can take a day or a week to resolve. If you are able, putting a poultice on the foot twice a day - something like a bit of cotton wool soaked in hand hot water - may help to draw out infection if it is an abscess.
If it started with a ripped hoof, it may be that some infection is sitting in there and will take a while, and perhaps repeated injections of antibiotic and painkiller may be necessary. (every 2-4 days depending what your vet has used, ask them when would be suitable to repeat) It may also be that a damaged foot means that she's tweaked or sprained something when she hurt herself, so time, painkillers and a bit of TLC should bring her right. There may be some soft tissue or the like damaged irreversibly, but as long as she seems reasonably comfortable, eating, getting about etc, then she should be OK.