For a while, I thought she was in a hospital with a head injury before I realized that's probably one of those head bands, lol. OTL
I love the vector; it's really pretty, vibrant and colorful with enough details to make the characters stand out. The roses add up to that feel of manga panels and sparkly shoujo scenes, lol but somehow, those text bubbles seem kind of out of place. Perhaps just adding text without the bubbles would be enough - with them looking like this, it's like they take too much space and take the attention away from the scene/characters.
Still, good job! I have no idea what the series is about (well, tennis, obviously but yenno... xD) but overall, it all looks nice. Keep it up!