Keep in mind I’ve never personally dealt with a stifle injury, just other stifle issues, but IMHO, a true injury such as what you have needs, as previously stated, total stall rest for some period of time, no hand grazing, no hand walking, not even putting her in the aisle for grooming. The knee/patellar joint is inherently delicate, relatively speaking, and damage to it increases that instability exponentially. The only question is - how long for total stall rest before another set of xray is take to gauge healing? For that, I still think you need to get the original set to New Bolton or somewhere competent, and get a much more educated and willing opinion than your vet is willing to give. They can give you some guideline like “total stall rest for 3 months, then get new rads and we’ll re-evaluate at that point”. Stifle injuries are like suspensory injuries - you should really not judge healing based solely one external appearances.
Also IMHO yes to some NSAID as stated above. If you decide on Previcox you’d be off-label using a Rx for one of your dogs - can’t get a legal prescription for a horse for that But it’s cheaper than Equioxx, so… And yes, to Pentosan, or even start with a full loading dose of Adequan first, then switch to Pentosan. Anything you can do to support the joint is good.