This is very simple.You file eviction.Go to court.When you stand in front of the judge present the facts.Be emotionless when you speak and have timeline in a clear,concise,and quick manner.The judge listens to all kind of long BS all day long and when they get someone who keeps quiet and gives and quick and concise response you will stand in good favor with them.I usually let the tenant dig a big hole for themselves and it works every time.The less you can say is better.The judge has heard every excuse before and will quickly dispose of the tenant.Usually after the judgement is entered you can pay for a writ where the marshall will come and throw the tenants stuff out.Depending on how many writs they need to serve that month it could take 3 to 4 weeks to get them out.The tenants do not know the writ office is back up so most leave right away.Here if 500 or less of property is left and it appears they have abandoned the property you can re-key and throw the stuff out.Here if they do not file an answer in Georgia for the court you can get the writ but not a judgement.I would have to pursue them in small claims court then.So as you can see it is vary important to learn processes for your state.I condition tenants before they sign a lease.No drugs,smoking inside,sex offenders,felons,aggressive dogs,etc. will be tolerated.We do inspections once a month and if ANY lease provision is violated we evict immediately.Everyone of my tenants pays on time now and the others have left.It's kind of like having a slack employee trying to get away with stuff all the time versus a great employee that works hard.

If the key don't work, bring a locksmith. 

If all else fails, once you are the owner, just have a locksmith come out and let you in. 

If the tenant that resides there still gives you a hard time, have a locksmith handy along with the police. 

When a tenant moves out we immediately rekey the tenant to our "hammer key" which all of our trades and cleaners and maintenance folks have a copy of-- the key is shaped like a hammer so they usually don't lose it or get it mixed up.

Thankfully I rekey all my locks between tenants. 

There a locksmiths that will inspect your property and complete the required rekey for you.

Ask them how many contacts they have of handymen, cleaners, locksmiths.

He tells me, locksmiths gets paid, plumbers get paid so why shouldn't he?

Did she have roommates, did your contractor maybe go ahead and rekey, or she is simply lying to get more time to get her belongings out??!!!