The phrase thanked her for her guidance is a pledge.
Step-by-step explanation:
A pledge is considered as a promise as well as a commitment for doing something. A pledge is mainly considered as a serious formal promise. A pledge is taken to show respect for a country, A pledge is taken to keep a secret.
A pledge is considered a verb as well as a noun. One of the example of a pledge is that my father promised me that he will buy me a laptop.