Internship advice?

Hi Guys/Gals,

I am in need of serious advice. I recently applied to an internship in late April. The women that I spoke with via the phone sounded really interested in me and ask me to follow up as soon as classes ended( around mid may ). I reached out to her early June and she stated that she would send me an offer letter in a couple of days and that she was very sorry and stated how busy her current schedule is.

Fast forward, it has been almost 3 weeks and I have not gotten a letter nor an update about the internship. Should I follow-up one more time or simply call it quits and move on?