Air-Geko: Had their been another bag to divy some of the other stuff into, it would have been fine. Unfortunately, it's rather tough to buy an additional suitcase in Cleveland at 5am... So, two checked bags (instead of up to four) and a nice dip into their bank account...
You say that there were two bags totalling 100 lbs, so Mother had to pay for 30 lbs excess. But if they'd been able to use both allowances they'd have been 40 lbs inside the allowance.
I therefore inferred that the limit was 70 lbs each, total 140 lbs.
So why didn't they put 50 lbs in one case, checked in mother's name, and 50 lbs in the other case, checked in daughter's name? Each of them 20 lbs under the limit, neither breaching the 50 lbs per bag limit (if applicable).
That's what I don't understand. Not having a go, just in complete confusion over what happened.