2:58 for the marathon equates to a VDOT of 54. The training intensity for that VDOT says 1200s at 4:25 and 400s at repetition pace in 82. You don't do volume work at R pace (it usually is capped at 5% of your weekly mileage or 3 miles), so you won't be doing many fast intervals. You'll do some, but you won't be running 1200s at R pace because the focus of such pace is anaerobic and therefore extremely demanding on the body. Your recovery is going to be up to 4x as long as the interval itself.
I strongly disagree. You will benefit from doing some fast intervals. The "you don't need to run any faster than x pace" train of thought is silly, in my opinion. You should strive for balance and for working on all aspects of your running, and from the looks of your training schedules over the past year, I'd say your coach thinks so too.
When you start to run faster than a defined pace it is either counterproductive, because you are working too hard and not recovering and hence not maximizing the benefit of the workout, or it is because you are getting fitter. You have to know when the faster pace is based upon fitness and not because of the thought "I want to get fast, therefore, I need to run faster."
The workout being discussed here equates to a 52 VDOT based on her 1200s and the fact she could not break 4:30. Interval pace of 4:33 per Daniels VDOT tables shows me a 52. The real issue here is the recovery time. 2:45 is pretty short for this and may be the determining factor in why she could not break 4:30. Recovery should have been around 4:30 after each interval.
Bottom line - Tim is correct about increasing the volume and not the speed, but that also means the pace of intervals will be slower. The key is to determine whether the workout is focused on anaerobic development (R pace with max interval of 800), VO2 Max which (I pace with max interval of 1200) or a threshold workout which is at tempo pace (T pace is 90% of VO2 Max). T pace is where you add the volume. If it is turnover you are working on then I or R pace may be proper. Most marathon plans focus less on R and I because your use of those components in a marathon is minimal, whereas 5K training will have a lot more R and I.