My baby girl of 7 months keeps crying in her sleep ( hysterically) and sometimes i cant calm her down and have to wake her before she stops crying.

Sleep issues: When an infant or toddler does not awaken immediately to your touch, they are not having a nightmare. The process is called a night terror & is a much deeper stage of sleep. It often happens when they have poor sleep habits or are sleep deprived. If you watch it & let it pass, they won't be confused when you wake them. Improve their sleep duration & it should pass. Or see their doc.