You might consider that if the current gains are significant enough. As JTs, there is a step up on 50% of the assets. Should you pass first (and the gifting of her share to you was completed more than 1 year before your death, there would be a full step up at your death. On the other hand, should she pre decease you, this backfires and there is no basis adjustment at all upon her death.
These rules apply per asset, not per account. Therefore, if you proceeded you would leave any assets with little gain or with losses in the joint account. If the basis adjustment is a “step down”, better 50% than 100%.