I know it might sound scarier with the urgent referral but it's good for her not having to wait so long, I've had three urgent referrals and each one has turned out to be something completely benign, mainly (and Sqad is going to tell me off if I spell it wrong again haha!) fibrous adenomas.
Things like hormonal changes can play a part, she isn't pregnant by any chance is she as that can cause breast changes.
I've always found the staff excellent and the results through very quickly. There may be a questionnaire to fill in so worth asking about any kind of family history so she is prepared for any such questions. I saw a breast surgeon on each occasion, had a fine needle biopsy and ultrasound scan done on two so plenty of time should be allowed.
It's far more likely to be something benign, especially if she's young.
I wish her all the best x