If you want me to be honest with you, I'd suggest keeping the "cute paragraph" that you want to send your girlfriend short and simple - especially if you're sending it to her in a text message or on Whatsapp etc..
Here are some really good ideas:
1. Use a picture
We've all seen them on Tumblr, the kind of love quotes that people share about their girlfriend/boyfriend.
Think how much your girlfriend would love receiving something like that, with a background picture of the two of you!
If you're stuck for inspiration, take a paragraph from her favorite song or rap lyric, and make it your own. Switch up the words so it's unique to her, but still shows you know what kind of music she loves.
3. Be yourself
If all else fails, just be yourself.
She's your girlfriend for a reason: Whether that be your way with words, how funny you are, or whatever... Let that shine through in your cute paragraph. Own it!