i would bring her to the doctor just to be safe. babies at that age arent "afriad" in the way older children/adults are so experts dont believe they have nightmares that young. what you described sound more like a pain cry, poss gas, but it really sounds like teething. babies go to sleep, then when the pain hits in the light sleep mode, they feel it enough to wake them up, but when they are in deep sleep, its just not painful enough to wake them. then add in the fact that they are soooo tired and got woken up, more crying.
i dont believe in crying it out, no matter "why" the baby is wanting comfort ie they are scared, in pain, cold, wet, lonely, ect, i believe you should respond. a babys cry is their way of communicating, esp to say they need you. i would highly suggest you respond to your daughter, she is crying because she needs you. now it might be because she misses you, or it might be because she is in pain. either way, she needs her mommy.
good luck, remember too she is at an age where she is learning or attempting so many new activities, her brain will be overloaded and her body achy at the same time she just wants to sleep. that too can cause sudden wakenings like you describe.