In general, "(と)～は言った" is also natural after a question, and people often use it randomly to avoid monotonousness. FWIW, in novels, some writers prefer 訊いた instead of 聞いた. (訊 is a non-joyo-kanji which is specifically used for きく in the sense of "asking a question")

In this case, まる子は言った would be better, because 「根っからのほめられ好きだね」 was probably said with a falling intonation, and does not sound like a true question. まる子は聞いた implies "～, aren't you?(↗)" (rising intonation).

In general, "(と)～は言った" is also natural after a question, and people often use it randomly to avoid monotonousness. FWIW, in novels, some writers prefer 訊いた instead of 聞いた. (訊 is a non-jōyō-kanji which is specifically used for きく in the sense of "asking a question".)

In this case, まる子は言った would be better, because 「根っからのほめられ好きだね」 was probably said with a falling intonation, and does not sound like a true question. まる子は聞いた implies "～, aren't you?(↗)" (rising intonation).