It means the young man is way beyond the girl's imagination of how a boyfriend could be. He is TOO good -- too good to be true (real). The sentence usually should carry a positive meaning, but it can also be used to mean something negative.

While it is difficult to say what someone else means by a statement like this that can be taken in a number of different ways, it's very similar to another expression: "If something seems to good to be true, it probably is." In that case, the meaning is that if something is such a good deal that it seems unbelievable, it probably is not true. Here, the meaning is similar: There must be some hidden problem with a boyfriend that seems so perfect. There is a problem that we can't see.

It means the current situation with her boyfriend, it's almost at the point of not being believable and it will soon fall apart. There's an expression called "If it's too good to be true, it is." In other words, be careful of things that seem so great, they can't possibly be so good!

To good to be true is supposed to be something said for something positive but most of the time used as a negative but in this case her to good to be true is a positive it’s everything she could ever ask for it’s her fairy tale her happy ending it’s like when something great happens to you and you think this can’t be happening to me but then if she is using this as a negative then it’s doubt in her mind cause she not used to anybody being this way and feel like he is being so nice and doing all this things for her to try to get something out of her which it’s not going to work out just cause of this doubts and make him not even want to do anything for her anymore which she can be like why don’t you do this type of things anymore and push him away but there can be couple different meanings for it just depends on the person and the situation

”好的离谱“，但是总觉得好成这样不大对劲，还是正常点，偶尔有点小脾气倒显得更踏实。