Hmm, my bf said it to me after like 2 or 3 months and I sorta freaked out. Not in front of him or anything like that, but I really questioned the sincerity behind those words since I wasn't so sure I felt it yet. Depends on the person though, some freak out majorly and feel trapped, while others can handle it in stride. Just don't make it uncomfortable for her, like when you part don't say "I love you" then add that dramatic pause and the puppy dog eyes, that causes the extreme cases of freak out.