After doing some research, it seems that the adjective טוֹב (tov) is sometimes used in reference to people in a manner referring other than to a personality trait (i.e., "kind").
For example, in Gen. 6:2, it is written,
And the sons of God saw the daughters of men, that that they were [טֹבֹת], and they took wives for themselves, whomever they chose.
וַיִּרְאוּ בְנֵי הָאֱלֹהִים אֶת בְּנוֹת הָאָדָם כִּי טֹבֹת הֵנָּה וַיִּקְחוּ לָהֶם נָשִׁים מִכֹּל אֲשֶׁר בָּחָרוּ
טֹבֹת is the plural feminine declension of the adjective טוֹב. It is being used to describe בְּנוֹת הָאָדָם (the daughters of men) as physically attractive (beautiful; fair), thus compelling the sons of God to take them as wives.(1) Gen. 6:2 contains the same basic syntactical structure as Exo. 2:2 (concerning the adjective טוֹב):
[subject] + verb רָאָה + direct object + conjunction כִּי + adjective טוֹב + pronoun
וַיִּרְאוּ בְנֵי הָאֱלֹהִים אֶת בְּנוֹת הָאָדָם כִּי טֹבֹת הֵנָּה
וַתֵּרֶא אֹתֹו כִּי טֹוב הוּא
Therefore, in the case of Moses, his mother saw (with her eyes) that he was physically attractive or beautiful (טוֹב), so she hid him three months. Unfortunately, the text doesn't offer any insight as to why his physical attractiveness persuaded her to choose a particular course of action, or what she would have done had he not been physically attractive.
(1) Gesenius, Heinrich Friedrich Wilhelm. A Hebrew and English Lexicon of the Old Testament, including the Biblical Chaldee. Trans. Tregelles, Samuel Prideaux. London: Bagster, 1857. On טוֹב, p. 318, §2. [source]