Clinical trials benefit future patients and medical researchers but you and your mom need to do what's best for her. There are two tradeoffs to consider: first the risks and possible benefits of the trial, and second the treatment she'd receive on the trial vs. the treatment she'd receive if she chooses not to participate in the trial.
Did her doctor recommend Clofarabine whether or not she's in the trial? If you don't know what non-trial treatment she'd get, it's worth discussing with her doctor, since you should know all of her choices.
There's at least one trial that will be testing the appropriate dosage for Clofarabine. Is that the type of trial she's considering?
Note that the correct spelling is "Clofarabine".