网友的句子通常的说法应该是：

What would she think if she learned the truth? 她要是知道实情会怎么想呢?

但也不能说网友的句子就一定是错的，因为在口语或非正式文体中有时也可见到这种用法（尤其是美国口语中，但正式文体或书面语中通常不这样用）。如：

It would cause a great deal of harm if this would happen. 如果发生这种情况，将会造成很大的危害。

不过值得注意的是，用 if...would 来表示意愿或礼貌性的请求则属于正常用法。如：

Eventually she struck a bargain with him. She would get him a job if he would help her with her singing. 最后他们讲好条件，他如果教她唱歌，她就为他找份工作。

I’d be much obliged if you’d hold the door for me. 如果你能帮我拉着门，我很感激。

I’d really appreciate it if you’d turn the TV down. 如果你能把电视声音关小一点，我会非常感激。

It would give me great pleasure if you would join us for dinner. 如果你能够同我们一起吃晚饭，那我真是太高兴了。

I’d be glad if you’d let me know when the meeting is. 如果你能告诉我会议的时间，我将非常感激。

We would esteem it a favour if you would settle this account forthwith. 如蒙立即将这笔账结清，将不胜感激。