There are Biblical reasons for divorce; there aren’t for fornication.
Divorce can be forced upon one, against their will, by the other party. What sin attaches to one for the sins of another?
Divorce, regardless of responsibility or reason, is forgivable upon repentance; and nothing ongoing attaches thereto, IF the divorced party then remains in their estate, maintaining chastity...she didn’t.
Are either of us privy to the details of her divorce? If not, then best not to judge on that basis.
OTOH, the fornication and pregnancy are undeniably upon her; and they are in contravention of her contract’s morals clause.
So now, we have to justify the school’s decision by hoping that the divorce was the husband’s fault. Face it, the school made a move based on PR and it is coming back on them.