At 18 months my daughter still had a very limited vocabularly and the daycare teacher even commented on it but assured me it was not unheard of and her language skills were simply developing later but othre skills were strong. She assured me that she'd be fine by kindergarten and wouldn't have any significnat delay. My neice who is 3 months younger was talking in full sentence at the time - but didn't walk until she was nearly 2. My daughter had been walking at 7.5 months (the earliest walker my pediatrician had even seen).
She had a slight delay at school age and we had her evaluated. The delay was not significant enough to qualify for services though.
My daughter is now 16 and her language skills are fine. Language skills have never been her strong point - and still arent' but she's has great math and engineering skills. Interestingly enough, my neice who was an exceptionally early talker but late walker, has been recieving awards for her writing for a few years now (poetry, short stories, etc.) but struggles with math. so it seems their skills and aptitudes show up early in life!
Maybe your daughter will be an exceptional architect or scientist! But I promise, there will be a day when she's asking you a thousand "why" questions or boring you to death about the newest "boy band" fan information that you'll look back to these days and smile.