If anything, they will be monitoring her much more closely than a woman with a healthy BMI.
She would or should of been refered by the midwife at the booking in appt, when she next sees the midwife, get her to ask about her referal, she should be sent a letter from the hospital with an appt to see a consultant.
She will also have more hospital appts that a 'normal' pregnant woman.
I have a bmi of 42, and am also under consultant led care because of other health problems aside from my weight, i found it lovely tbh, feel much more reassured, you get to hear babies hb a lot more often and i felt a lot more cared after.
A lot of my friends who have uncomplicated pregnancies, even their first felt like they had been rushed in and out of appts with midwifes, not had them at the time they should of had them etc.
I would just let your DD know, that yes, there are some significant rises in risks with obese mothers, but because she will be looked after very well, and often, she will get whatever help she needs asap.
You could also get her to ask about any pregnancy exercise classes arranged by the hospital that could help her fitness for labour etc, she has a little time to make some difference, even not gaining any more weight, or raising fitness levels will make a huge difference when the baby comes.