Earnings from personal injury settlements are generally not deemed income attributable to the other party for Child Support purposes. Only if she received a settlement that was payable as lost wages will it be considered. Usually such payment will not be designated as such.
Regardless of her settlement, you are seeking modification and thus have to prove a change in circumstances based on your loss of income. When seeking modification based on involuntary loss of income one should be prepared to show that the loss of employment was involuntary a letter or something terminating you or advising you that no work is available, that you are making efforts to replace that income by applying to jobs with equivalent pay and whether you have filed for unemployment. Such modifications are usually hard to obtain if expected to be temporary. i.e. you work for a union and are laid off on a regular basis.