How do we get her out of the house legally?

Half of her rights to what? Since she is not paying rent and is not a tenant but rather a guess, she has no right to be in the house if all owners tell her to leave. You could ask the Sheriff's Office to physically evict her, but they will probably say you need a court order for them to act [because they have no direct knowledge of whether she has a right to stay or not]. Ask them what they need. So you would have to serve her with a three day and thirty day notice of eviction, set the matter for trial, get a judgment, and then have the Sheriff evict her.