A google extension

I installed a google extensions that can help you to know who removed you from their friend list on Facebook. When it suddenly dawned on me that how useful this extension is, the extension told[2] me that her[1] ex-girlfriend removed us from her friend list. Because most of time you wouldn't check your friend list and find out who deleted you. But recently I found this extension has some problems[3] when it told me there is someone who deleted me. And after I checked that person's facebook friend list, I found I am still in their list! So maybe it needs to be repaired by their engineers.
Here is another following story. Today, when I was watching the website, the notice occurred again and there were 4 people that deleted me from their list. And after checking our relationship, I found that the notice was true! So now I'm curious about that, why recently so many people deleted me. Just because it is summer vacation so they want to clean their facebook just like they clean their room? LOL (Though they are people that I'm seldom contact with.) But when I go to the google play store to check this software, I can't find it.... It's really weird. So has the editor closed it but I'm still using the broken one?

And I have a question that I hope someone can advise me on:

"When it suddenly dawned on me that how useful this extension is, the extension notified me that her ex-girlfriend removed us from her friend list."

[1] who is she? you should introduce someone before using a pronoun.

[2] to notice is to see. A program can tell you something, or notify you of something.

[3] some problems or a problem.

To me - you haven't quite got the logic right there.  "It suddenly dawned on me that how useful this extension is, when the extension notified me that her ex-girlfriend removed us from her friend list." would be more logical. The way you wrote it, the realisation dawned on you, then it notified you.

Something 'dawns on you' when you suddenly realise something, which is usually in response to something happening. e.g. 'It suddenly dawned on me that I really had learnt to read some Chinese, when I realised I could read 4 of the 5 characters in the restaurant's name'. 'It dawned on me that she really did love me when I heard her talking about me'.

A google extension

I installed one of google extensions that can help you to know who removed you from their friend list of facebook. When it suddenly dawned on me that how useful this extension is, the extension noticed me that her ex-girlfriend removed us from her friend list. Because most of time you wouldn't check your friend list and find out who deleted you. But recently I found this extension has some problem when it noticed me there is someone who deleted me. And afterI checked that person's facebook friend list, I found I still in the list! So maybe it needs to be repaired by their engineers.
Here is another following story. Today, when I was watching the website, the notice occurred again and there was 4 people deleted me from their list. And after checking our relationship, I found that the notice is true! So now I'm curious about that, why recently so many people deleted me. Just because it is summer vacation so they want to clean their facebook just like clean their room? LOL (Though they are the person that I'm seldom contact with.) But when I go to google shop to check this software, I can't find it.... It's really weird. So is the editor closed it but I'm still using the broken one?