Ms Luge, as you call her, is not looking for her old job or seniority. She's trying to be part of the solution at Jetblue. Whether or not they make it or you approve of her "act", she knew the consequences when she bailed. She was not furloughed--she resigned--and that's a horse of a different color.
My own take? JB has communicated with its crew force, kept everyone in the loop, and generally tried to be a good place to work. If you think they have a chance at continuing to grow, or if you think the 190 rates will be adjusted this Jan (common speculation--I have no clue...), you may end up with a good place to work the next 20 years. Or--you might not. Its still a new company (geez...its only 6-7 years old..) and has a lot of challenges ahead.
United, on the other hand, is what is left of what was a glorious place. However--don't compare the company you are returning to with the one you left. QC the work rules, benefits, etc very closely. Also--United has proven when things get tough you are expendable. They are aggressively flirting with merging with someone or selling off some assets for cash flow. If you are just now getting recalled, you can pretty much bet you'll be at the bottom of whatever United morphs into if they merge. While work rules may be better now on the junior bus or guppy, who knows where they will go if United can't make money--and they have a history of being terrible at that.
So--its a tough call. I have no dog in this fight, and wish you the best. I've got 3 furloughed United pilots in my squadron, and all are bypassing for now. Their biggest fear is a merger while they are out. If you bypass another year you can at least sit and watch and get a better guess as to where each company is really headed.
Good luck...