The speaker is so taken with another person that they have to tell someone, and they choose the stars. They don't talk about looks or achievements. Instead they describe small, everyday things: the way this person laughs, cries, smiles and frowns. Putting the sad and annoyed moments right beside the happy ones suggests the speaker loves the whole person, not just the easy parts.
The ending is playful. The stars "clearly loved" the person, which is a charming way of saying the speaker believes anyone who heard about them would fall for them too. It also hints at how the speaker feels: the love is so big it seems to spill out into the sky. The repeated "i told" gives the poem a soft, confiding rhythm, like someone whispering a secret at night. The mood is tender, simple and a little dreamy, with no complaint or doubt, only warm admiration.