Well that depends on a few factors... first of all, progesterone checks are far from perfect and you can be checked at a low (even more than two times!) since your progesterone comes in spurts throughout the day and is not a constant level... so someone with the highest level of 15 could very well have problems but always test supposedly-good... and someone with a lowest level of 5 could have a highest level in the 20s range but consistently test bad yet be fine.
Secondly, most consider that anything over 5 means ovulation happened which is good enough, since at 7dpo many would not be implanted completely yet... so the levels could still rise once the corpus luteum gets the signal that pregnancy has been achieved.
Unless she shows other symptoms such as a short LP (most doctors consider this to be anything under 10 days) and as long as her doctor tests her levels again asap once she gets a BFP... I would say the doctor is just trying to keep her from adding a possibly useless medication to her system. (Yes. Possibly useless. If her corpus luteum does its job post-BFP she does NOT need progesterone. It doesn't really matter if it is producing levels of 25 before that BFP... as long as the embryo has time to implant and signal the CP to start producing more)
