My sister is receiving money from a foreign guy.

I have noticed that my sister has been buying expensive things lately. Last week, she bought an iPhone X and this week, she a new LV bag. I was wondering where she could actually get the money for those expensive stuff since she is still studying and although she has a part time job, it would not be enough to get such a huge sum of money to buy those things. Due to this, I decided to investigate because I was worried she's getting the money from illegal doings. However, as I did my investigation, I found she is receiving this money from a foreign guy twice her age. I want to tell her off on this but I can't because I don't want to offend her, something like that. How should I confront her?