Upon inheritance, as a devisee, you are entitled to continue to make the payments under the Garn-St. Germain Act without fear of the lender accellerating the loan. If you don't make payments, the lender can foreclose. The house will be yours, subject to the loan, and you can sell it, lease it, or live in it.
It would be impossible to be charged for trespassing because both siblings are owners. On burglary, there must be a breaking into a building with intent to commit a crime, and you can't break into your own property. If there is any doubt, contact local law enforcement and run this by them. I would suggest you both establish boundaries so that everyone can live in peace. For what it is worth, occupying sibling should "lease" the other's portion and pay rent while in occupancy for the...
I think you might not know the purpose of a lis pendens. It merely provides notice of anticipated or pending litigation and is filed in the real property records. It is merely a notice which is notarized and is recorded and serves no other purpose other than to provide constructive notice on record. On your other issues, my colleague offers excellent advice.
You can evict your friend. Be sure you give proper written notice and follow the instructions of the Washington eviction court. Many courts have instructions and sample forms at the filing desk or online.