How to ask friend for payment?

My friend who works for an international dating blog site, which I wonít mention, asked me to write a few articles for her. She said she had too many things to do with the deadline coming by so fast. She offered to pay me $50 for each 500-word article. I trusted her word for it so I took the job and even submitted it on time. She was so happy about it and said sheíll send me the details of payment once she has edited the article and was pushed live.

A week after submission, I followed her up if the article was okay or if I had to do any revision. She said everything went well and that she has already pushed it forward to her superiors. Itís been 3 weeks now and I still havenít heard from her about the payment. How do I approach her about the payment? Do I just wait until I hear from her?