In Engpsh, we might say that she is growing quickly or that she is developing rapidly. This phrase comes from the verb "to grow," which means to increase in size or to become bigger or taller over time.

Here are a few example sentences in Engpsh and Chinese to help illustrate the use of this phrase:

She is growing quickly, and I can already see a big difference in her height. (她长得真快，我已经能看出她身高变化很大了。)
He was a small child, but now he is developing rapidly and catching up to his peers. (他以前是个小孩子，但现在他长得真快，跟上了同龄人。)
The plant was only a few inches tall when I bought it, but now it is growing quickly and needs to be repotted. (我买这棵植物的时候它只有几英寸高，但现在它长得真快，需要换一个大点的盆栽。)