Internship/ full-time

One of my friends has got an offer from a startup where she has to intern for 3 months, and then it gets converted to full time. Its joining date is this coming monday. But she is expecting another offer, which is a full-time job. Done with the interviews, just waiting for the offer.

So can she join the company as an intern for now, and until she gets a joining date for another company that is offering a full-time job,will it cause any issue in BGV later ?