An adverb can modify a verb, an adjective, another adverb, a phrase, or a clause. An adverb indicates manner, time, place, cause, or degree and answers questions such as "how," "when," "where," "how much".
If I had to pick just one sentence, I would opt for:
"Lately, I have noticed a change in her appearance."
Here is a great site that explains adverbs quite well. What is an Adverb?