Paul84, here is some pretty standard info I give for investigating cheaters. Use what applies to your situation to find out a whole lot more than she is willing to tell you:
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1) GET ANY INFORMATION YOU CAN FROM HER PHONE
a) Check her phone bill to see who she has been texting and calling, how much, how often etc. See if there are any numbers she has been calling a lot that are suspicious, basically, her ex-boyfriend. Run the number(s) through a reverse lookup like spydialer (dotcom). Find out further information through fastpeoplesearch (dotcom) and/or truepeoplesearch (dotcom) which are both free, or if you really want to learn more, try truthfinder or beenverified, both online, beenverified you can find a promo code to make it like $3 for a 5-day trial.
b) Get her phone in your hand and look through her texts, any other messaging apps, photos and videos.
c) Buy the phone recovery software "Fonelab" and run a recovery on her phone to capture any deleted information such as text messages, photos, videos, cheater app messages, you'll also be able to see her notes, calls made and more.
d) Collect that evidence, and store it away safely! If you run a recovery the evidence will be saved to your computer. Otherwise do it with screenshots that you send yourself.
BONUS
e) If she is on an iPhone and you have another apple device, you can add it to her iCloud account and then you will see all her iMessages, and if you do it correctly, her SMS messages as well, in real time as they appear on the device in your possession. Be careful, adding a phone to an iCloud account generates an alert on the main phone so have her phone in hand when you do this and dismiss the alert.
f) If she is on an iPhone see if you can get into her iCloud account and maybe you can retrieve her iMessages. Be careful, accessing iCloud generates an email to the account holder so you must be prepared to intercept and delete that email.
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2) SIMULTANEOUSLY GET A VAR OR TWO (VOICE ACTIVATED RECORDER)
a) Get a couple of VARs (Voice Activated Recorders) the Sony ICD-PX470 is the sweet spot $50 at Amazon, put one in her car and keep another around to record her in the house.
The point here is to hear what she says when you are not around, particularly afer you confront her and she is panicking. That is when cheaters run to their car and call their affair partners and partners in crime.
b) Read the manual for a couple of minutes and you will learn how to turn off any kind of beeps or lights.
c) Get a ton of triple a batteries, Amazon brand (about $14 last I checked.)
d) Get a Sandisk 32 Gigabyte MicroSD card for each VAR, about $8 on Amazon and you'll have dozens of hours of recording time.
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3) IMPLEMENT PHONE MONITORING
A) Implement some kind of phone monitoring service: mSpy, ikeymonitor, cocospy, Flexispy, webwatcher, there are a ton of them.
These services allow you to monitor all kinds of phone communications in near real-time.
If you go this route you don't have to add a phone to her iCloud account.
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4) PUT A KEYLOGGER ON HER LAPTOP
a) Since you busted her on her laptop, a keylogger is a must. put it on before she changes the password.
I've used "bestfreekeylogger", but if she changes her password, you cannot get to the information. I've head good things about "Webwatcher" (Who also make phone monitoring software) and "Spytech SpyAgent"
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5) MAKE HER GIVE YOU A NO-BULLSHIT, NO LIES, NO EXCUSES, NO BLAMING YOU, DETAILED TIMELINE INCLUDING ALL THE GORY SEX DETAILS
a) If she wants to stay with you demand a detailed timeline that she will write immediately
b) Find a reputable Polygraph operator and tell her you reserve the right to verify it via polygraph.
I would tell her after she writes the initial timeline and then watch her run back and amend the shit out of it.
Others might advise you to tell her prior to writing the timeline.
c) The purpose of the sexual details is for you to really really know what went down and for her to stop living in a fantasy land of a "beautiful romance that was meant to be".
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Do these things and you will know what you need to know.
Best of luck to you Paul84