I had a baby 13 months after my first c-section. I was not advised not to have another quickly, but my second was neithet planned nor unplanned - we had fertility problems the first time, so preferrred just to let nature take its course.
I was told that I may need another section, not only for the fact that the scar may not stand up to a delivery, but that the reasons for me needingh asection in the first birth may reoccur - which they did and I had a second section.
The consultant said that she was glad she had done the section as it was apparant during the surgery that they scar would not have held.
If your daughter is pregnant, they will monitor her closely and make a decision nearer the time whether to let her try for a normal delivery or not. They will then keep a close eye on her during the delivery.
I would tell her not to worry, but to prepare herself for the prospect of another section.
My second section was a lot easier than the first as it was planned and was over very quickly - I left hospital after 2 days.
I was asked after the 2nd about whether I was planning any more - which I wasn't!!