No, they will not allow a child who dosen't meet the height restriction to enter the line.
I was in this situation last year as the solo adult with my dd's. My oldest, then 10 yo really wanted to ride and had many times prior but my youngest wasn't tall enough. My 8yo was not allowed in the ride line at all, no way no how! FWIW, the CM understood my dliemma and was kind about it but he just could not do it.
My 10yo was ready to ride alone or with a stranger on the coaster but she wasn't comfortable doing the entire line alone so she skipped it. I did give her the choice as I could see most of the outside line and I thought she could handle it.
Sorry, HTH
TJ