Yoko [subject-が] that-way say-[nominalizer-の] [also-も] reasonable is.
そういう ('that kind of / such a way') + 言う = 'speak that way.' The のも is nominalizer の + 'also.' もっともだ ('reasonable / justified / no wonder') is a set idiomatic predicate. が marks Yoko as the specific subject doing the saying.