I am sorry that you also went through this. HELLP is indeed a serious condition. Unfortunately, medical professionals don't know the exact cause and many symptoms also correspond to other complications of pregnancy. I think the best piece of advice is "when in doubt, head to the hospital" - the worst thing that can happen is that you are sent home. We were (as you read) not sent home and have a happy, healthy toddler now. HELLP can manifest in many ways and is probably wider spread that statistics may show. It is important for women to be in touch with their OBs/midwives throughout pregnancy and at the first sign of labor (especially in the first full pregnancy).
Best wishes to you,