Yep, if the race intensity is high early on, then a good warmup is a must. Not just crits. I did a road race last weekend that had a steep hill only 2 miles into the race. As a result there was no nice roll out, rather a fast pace to the hill, then drilling it on the hill, then going harder after the hill to take advantage of gaps. A warmup was defiinitely in order for this race.
My MO has been a slow starter and strong finisher. Believe me, I've been trying to figure out the proper warmup for a long time, and I'm still learning. In cyclocross races I often experience what I call "2nd lap blues", where I start losing ground. I'm usually able to regain form and ride the strongest in the last half of the race though. I can only conclude that my warmup just isn't sufficient.
I've tried to find out ways to quantify when I'm warmed up better. One thing I've noticed is that when I monitor my heart rate during a warmup, my "perceived effort" seems much higher at a lower heart rate when I'm still "cold". So, one way to know when I'm getting properly warmed up is when I get that heart rate up close to LT/AT and it starts feeling more like "steady state" rather than "max effort". It can really vary as to how long it takes for the warmup to get me there. Sometimes I just don't have the time, and then I'm forced to get there during the race.
The race you mention is so short such that a warmup could be really beneficial, if she really wants to go for the big win. BTW, I've also found that stretching beforehand doesn't really help. In fact it sometimes makes things worse, e.g. lower back starts stressing out sooner. It's better to warmup slowly and get the blood flowing before doing much stretching at all. I've found stretching after the race really helps though.