One way to prepare a seller for the sale of there home in advance is to have the seller start packing their personal belongings and if they can't afford a storage unit, then put the boxes in a spare bedroom. This starts the psycological process of changing "their" home to just a house. For you I would suggest you might make reservations in temporary military housing on a near by base, so that if a problem does come up you have a place to stay for your family, assuming your person effects will be shipped and stored til you get them, this will ease the stress of having a place to live when you arrive. Don't worry. Your agent seems to be handling what ever has come up. That's why you have an agent to represent you. Best wishes in your new home.
Real estate transactions can be stressful enough on their own, you can't worry yourself with the seller's emotions. The Realtors are paid to deal with that. Do your standard inspections, negotiate in a way that works for you, and try to close the transaction.
Without being a real estate attorney and never looking at the contract or knowing the exact terms; I cannot advise you of what you should do, but I do know that with some of my previous transactions we have "forced" the seller to close. It's usually not very pretty and certainly not a position I like to be in, but we represent our clients and we do whatever may need to be done to get it closed.. If she still refuses, then I believe you could sue for actual damages "fees, cost of staying in hotel until you close on another home, etc." That would definitely be a question for a Real Estate Attorney.
It may just come down to how much you want this home. Is it the home you see yourselves in for 10 years or was it a "quick fix"? It may be that there are others out there that fit your needs even better. You may have your agent do a search of available homes as well.
Good news is that it is the perfect time to move here. We are toward the end of the rain and will have a beautiful summer! Being that close to Lake Tapps will be a great benefit to you.
Good luck to you!