High Risk of Fraud Detected but it's a Repeat customer

[TommyDAQ]

I just recieved an order that Shopify flagged as High Risk. According to the Fraud Analysis Indicators, it says that:

• Negative
  Characteristics of this order are similar to fraudulent orders observed in the past
• Negative
  A high risk internet connection (web proxy) was used to place the order

The order was for two POD shirts, same color, same design, two different sizes (S, and M).  This customer also ordered the same product a month ago in a different size (XS). Same shipping address. Same email.  Paid w/ CC. 

The customer subscribed to my mailing list from my Klaviyo pop-up on my Shopify site. 

I've looked up the customer on Facebook. She appears to be a 65 year-old female, dog lover (my target market). Her account dates back to 2011. 

How do I go about Verifying the transaction. Why does this look high risk? Is it because 2 of the same shirts were ordered in two different sizes? 

Please inform and advise.  Thank you, 
Tommy

[JoesIdeas]

I would contact the customer, this is what we used to do when I ran a store. You can usually get a read on that. If they're non respondent or combative or have strange answers, we just cancel the order. If they give a legit reason, they we would let it go through (depending on other factors, but in general we could tell from the conversation).