I'm bilingual in Japanese and English.
I believe you are referring to the song, Osaru by Midori. Let's break this down into individual words/phrases:
あの娘="that girl/that chick". 娘（むすめ）can also be read as こ, and it sounds more "pop"
～はちょっと手強いぞ="[she] is a bit difficult". 手強い（てごわい）means formidable or difficult. This could mean that she is hard to get, flaky, or simple difficult to deal with. From listening to the rest of the song, it seems she is a bit crazy (in a fun way), and difficult to tame.
キラキラお目々を光らせて="with sparkling eyes". キラキラ is onomatopoeia/sound symbolism describing something bright and sparkly. As you may know, Japanese onomatopoeia also include things that don't actually make sounds. This is one example. She has sprakling eyes, which draw people's attention.
Hope this helps.
So you know the song. :)
I like that band, but I prefer Usagi. Do you know that one? They have a similar sound, but there is something weird about Usagi.