Did she cheat? - "I am just confused and can use some advice"

I was recently married and things were going great. My wife started acting distant and was just not the same.

She had gone though a rough time last year with a death of a close family member and with the holiday's coming up I thought that could be it.

I know she had texted one of her close friends a lot last March so I wanted to look in her old cell phone to see if I could possibly see what she felt back then so I can figure out what is going on now.

I found some very explicit texts between her and her ex boyfriend, which she has not seen in over 10 years.

He did a friend request on Facebook and she accepted it even after I asked her not to. I knew what he wanted and she said she was sure he wanted to be friends.

Well the texts I saw proved it was more... they talked almost everyday for a two week period and the texts were sexual in nature. He said she left him "hard", asked if she rememeberd what they did, and she would respond "mmm mmm mmm :)" She would tell me that he called and they talked but never about the texts.

One text he asked her to meet him and she responded "I will... I promise"... He even called her while we were at the mall looking at engagement rings!

She never hid the fact they talked but not to the extent that they did and about the texts. I confronted her about the texts and she said she was only goofing around with him and thought he not not serious about it.

She admitted she was wrong and she swears they never got together, had sex on the phone or that she never had sexual thoughts about him.

I asked her why she did it and she just says "I dont know"... She said he tried to sow the seeds of doubt in her mind about us.

We are not married but I am having a hard time trusting her. I keep seeing the words in my head and thinking there has got to be more.

She said at the time she was confused, the funeral was coming up and he did ask for her address and she would never give it to him. He wanted to send flowers "to the family".

When I did ask her to stop talking to him she did and they have not spoken since. Should I trust her that nothing physical happend?

She keeps saying she was sorry and that it was not a big deal and the texts meant nothing but then why do it?

I am just confused and can use some advise.