The real question here is why she knows Dash’s birthday. Tiara is a closet Dash fan?

Tsundere mode ACTIVATE!
 
She helps Scootaloo not feel like crap, by making her feel like crap, by reminding her that her idol’s (and honorary big sister) birthday is coming up so as not to come off as sympathetic she hides her affection for Scootaloo by seeking her out at her clubhouse for the sole purpose to bring awareness to something that’s more important to Scootaloo then another way to try and force a cutie mark before its time.
 
She gives her message, and trots off to let her plan something for RD’s birthday party.
 
Good, Bad-Filly, Diamond Tiara. Always indirectly guiding the CMC towards the path of righteousness. xD
 
You’re welcome, Bank Flank!

this is proof of the illuminati conspiracy  
no other way something like this would keep getting approved
 

@Jarkes  
Most likely low quality scanner or printer job.

You have to admire DT’s willingness to research things that would ruin the CMC’s day. She may be a byayh, but dammit she’s a professional one.

Why does DT look so PURPLE?

How…helpful of you for reminding them of Rainbow Dash’s birthday, Diamond Tiara.  
I’m so confused.

I’m not exactly one to be excited about THESE kind of comics, but I AM curious as to how this will go.

Scootaloo’s face in panel 4 = perfect reaction image XD