DD is a theme park pro and the only ride to ever upset her was Tower of Terror last year. She hated it and doesn't want to do it again. It wasn't the dark, it was the drop. How intense is the Mummy? She loves coasters.
It depends on the 7 year old. My nephew rode the Mummy last year when he was seven and loved it. He is quite tall and also rode the Hulk and Dueling Dragons and loved them. I actually thought the dark and the effects on the Mummy might be too much for him, but he went right back on!!
DD (6) loves coasters and can't wait until she's tall enough for the Hulk!
DD would hate the Mummy because of the dark but don't think the drop would be any problem at all
From what you said I think you'll be fine.
There are no big drops in the Mummy and unless you're daughter is afraid of the dark (or the Mummy) you'll be fine.
DS (10) felt let down by the Mummy as he was expecting more of a rollercoaster thrill like RNR. Once he decided it wasn't another RNR he actually found it good fun
I don't think it will be a problem. As was said, no big drops. My DS 7 also loved it. He was scared to death on Jaws and refused to ride it again (go figure???), but he loved the Mummy.
My DNeph(7) is not the 'bravest' rider and really had to muster all of his courage to try this one with me - but he did and said on the way out that he loved it - so I said, "let's go again!" - and he said, "not now, I'll go again next trip !"
My 6 and 8 year olds go on it all the time. 8 yr old loves it...haven't found a thrill ride she doesn't like yet. 6 year old loves the coaster part but not fond of the mummies. But she goes on it over and over again. She says the same thing about ToT- she likes the ride just not the effects.
I think she will be fine. It is so different from other coasters it is worth getting her to try it.