oh,yes---well the fact is that my young lady is much younger

完全可以.
1、than 从本质上来说是连词, than 后应该连接一个表示比较对象的主谓结构省略句.如：
Bill is taller than Tom is (Bill 的身高与 Tom 的身高相比)The fact is that my young lady is much younger than I am (lady 的年龄与 I 的年龄相比)He studied harder than I did. (He 的学习程度与 I 的学习程度相比)I have more friends now than I had before. (I 今年的朋友与 I 的过去的朋友相比)The news surprised Pat more than it surprised me. (消息让 Pat感到惊讶的程度与让 I 感到惊讶的程度相比)
2、考虑到比较从句中出现与主句重复的词语,为了是句子更加简洁,于是在应用中常常把重复词语也省略掉.如上述句子就可以省略如下：
Bill is taller than Tom. (than 从句中省略与上文 is 意思重复的 am)The fact is that my young lady is much younger than I. (than 从句中省略与上文 is 意思重复的 am)He studied harder than I. (than 从句中省略与上文studied 意思重复的did)I have more friends now than before. (than 从句中省略与上文I have 意思重复的I had)The news surprised Pat more than me. (than 从句中省略与上文The news surprised 意思重复的 it surprised)