What should she do?

Hey this is fire boy 11 again and most of my previous posts have been slightly on the serious side, So today i'm going to talk about something on the lighter side. I was talking to my friend the other day, and she brought up a good topic. The topic being is best friends going out a good idea or not. Since i don't have anything else to talk about, here i am. And before i start I would like to say that I am in tenth and when i state my reasons i am just referring to people in and around my age.
I have mixed feelings about this topic so I am going to write down my for arguments as well as my against topics and you can decide for yourself if best friends should go out.
Right so first my for arguments. I think that best friends going out is ideal mainly because best friends know a lot about each other already. Therefore they will know what they are getting into. They will know of each others past relationships so there wont be anything new. Also they are comfortable around each other and enjoy each others company. They can also freely talk to each other about anything, problems, thoughts, emotions, dilemmas etc.
 Secondly best friends have stayed with each other during hard or trying times providing support to each other, and therefore are best friends. The point I am trying to get at is there reliability has already been proven. Sadly those are all of my for arguments.
Now the against arguments. My first argument is that some boundary has to be drawn between best friends and girlfriends/boyfriends. Conversions with best friends can range from the mornings meal to recently seen movies to something personal. However a line has to be drawn when talking to your boyfriend/girlfriend. It has to be kept in mind that best friends are going to be those who stay with you for  longer while your relationship with your boyfriend/girlfriend is most probably temporary. You don't want to tell your current boyfriend/girlfriend something too personal. Something you will regret telling him if you break up. Especially if the break up is harsh.
 Secondly, considering you do go out with your best friend if the relationship ends badly then you will most probably be bidding goodbye to the great friendship which you initially had. Not only this, as mentioned earlier she/he may go out and tell everyone something personal you told them back when you trusted them.
 Lastly, as i mentioned earlier, i think that a best friend is someone you should be able to talk about anything, *including* the problems in your current relationship. If you are going out with your best friend then i don't think you will have anyone to talk to about the problems in that relationship as your best friend is the person is the person you have a problem against. Some may argue that if there is a problem then it should indeed be talked out and sorted by the two of them but i really feel that before this is done you must consult someone else in case you are planning to do something, what you call 'rash'. But as pointed out earlier now since your best friend is the the person you have a problem against you don't have any 'best friend' to consult first before talking about your problem.
Right so here is the deal. This friend of mine has been friends and good friends at that with this guy for over two years. Now she realizes that she likes this guy. She doesn't think that she should tell him as she thinks that it will ruin their current relationship as good friends. I have put up a poll on the right, please vote and also leave a comment. While you are at it hit the follow button. And lastly i would like to say that this situation isn't something that is happening to me. Just in case you thought that....