Must...Not...Click..."Proceed To Checkout"!

I have this shirt sitting in my shopping cart at 80's Purple :

Above: Women's Scoopneck Sequin Top (Cream/Taupe) by Aryn K

It would be so great for going out at night...only I haven't anywhere to go out at the moment in this town.

Look at the close-up of the front:

Above: Front detail of top.

I am loving it a lot! The minus...it is $50 before shipping.

Above: The backside of top.

I am so close to clicking "Proceed to Checkout" and the only thing holding me back is not knowing if I take a size "Small" or size "Medium".

I am just loving it and wanting it.