Answer:
Well, there is no adjective as a single word - if that is what you are asking for. Instead, there is an adjective clause (which serves as an adjective).
The adjective clause is: 'who will teach you.'
Step-by-step explanation:
The adjective clause 'who will teach you' describes the noun girl. It's the equivalent to saying this sentence:
adj. N
Kayla is the "teach-you-how-to-swim" girl.
Does that make sense??