UPDATE: She blew an abscess from her back right foot yesterday. Previously the lameness was in front but suddenly switched to the back yesterday. The vet was back out today and confirmed the abscess, however we are still treating for laminitis as well as she was sensitive to varying degrees in every foot with hoof testers. More sensitive on the right side than the left. Her hoof is packed and she’s moving better today.
I hope your farrier is picking up on the possible laminitis. You can actually see changes in the wall at the bottom of the hoof after the trim - you will see honeycomb like markings that show up after the laminae has been corrupted.
Early warning signs include crestiness and firming up of the crest (it feels very hard), and the horse/pony becoming foot sore. This is hard to determine when the ground is frozen since they all walk a little gingerly on frozen uneven ground. But if the pony is a bit footsore and the ground is not frozen, suspect laminitis.
When the horse has a hind leg problem, it will sometimes look like it is lame on the opposite front leg. But with your horse being lame on the right front and right hind, that is probably not the case.
Horses with chronic low grade laminitis will abscess more frequently. So you may have chronic low grade laminitis, which may usually present in the front feet (sometimes more on one side than the other) but it is present in all 4 feet, which explaines the hind abscess.
Or, the feet are just a bit bruised and sore from the frozen ground, which can also result in an abscess.
But whether it’s laminitis or bruising, your farrier should be picking up on it and asking you about it.