Recently I have had numerous insecurities and issues with my fiancée.

I found that she had been talking to other guys about getting together with her just to hang out and go to dinner. My problem is that I'm old-fashioned and believe that, if a girl is married or engaged, she should not be going out with single guys. Then I find out that this guy is interested in her and has feelings for her. Now she is mad at me for not liking the situation. This is after the same thing happened with a second guy that she actually sent personal pictures of herself to.

Should I be insecure or jealous with this? Or am I within my rights? She is quite mad at me right now and says that I need counseling for my insecurity and that she is not going anywhere, but just likes the attention. By the way, we are both 29 years old.

I would talk to her.
How her behavior isn't working. This could end up being nothing.
Find out for sure.

I wouldn't rush into anything until you sort this. Either get on the same page or split.

"This is after the same thing happened with a second guy that she actually sent personal pictures of herself to. "

That's not cool. She may not be as serious as you are. Doesn't sound like it to me.
How long have you been together?

If this arranged, you may want to get more specific advice in that area.

Forget her. All the females in the world and you give your heart to one that doesn't deserve it, nor knows what to do with it! NOT Smart of you, my friend.

We do not have her side of the story so we can only go by what you have written. Has there been other issues in the past that has caused you to be paranoid or insecure in this relationship? How long have you known her for? What is the history between the two of you and with past relationships? How do you know if she has been talking with other guys? How do you find this out? Do you question her all the time about everything? If you do then you are actually creating your own problems with her, by pushing her away from you.

Now I am done playing devils advocate,
Your old fashioned. She is going out for dinners with other guys just for liking the attention? Do you not give her enough attention?
Either way she may always always like this attention whether she is engaged or not. It is up to you whether it is okay with you or not.

It sounds to me that this behavior is not okay with you. That this behavior does not belong in your relationship yet she continues to do it and then tries to blame you for her own behavior. Do you think that is fair or right of her? I am thinking not.

She wants you to go to counseling, if she is so brave to blame you for everything. Why not go for counseling but tell her that you will not go to counseling without her with you. See if she is willing to go with you. If not, do not even bother.

She will have to seek her own help in the attention of other guys while you learn from this experience. Grow from this experience and maybe one day you will meet that girl of your dreams that you both enjoy each others company. That you grow together. There will always be those nagging questions as long as you do not continue or let these insecurities from this experience carry over to another relationship down the road. Does this makes sense to you?