Sym is a lonely girl, but she seems to have at least two friends who aren't imaginary. The first is Maxine, who's really more of a frenemy than a pal. She's more sexually mature than Sym, much to Sym's consternation. Maxine knows it and flaunts it, frequently teasing Sym about her disinterest in the opposite sex.
Sym is also friends with Nikki, who she seems to like better. But Nikki, in her brief appearances in the book, has little personality or affect. "Whenever she speaks, there's no sign of an exclamation mark anywhere" (1.37), Sym tells us. This, we glean, is preferable to Maxine's teasing.