Bell can listen as fast as she can read. Paper would be better for recording her life, but with her nifty little device, it's a close contest; besides, she's used to this. She glances at Sherlock occasionally while she directs the playback to skip around, reviewing this chat on physics and that on why Panem is economically implausible and the other on what books she ought to read (she thinks she's read them all, now, but she may as well check again if she'll be ushered back to Milliways at any moment.)

Usually Bell doesn't even reveal the recorder's existence in front of anyone. Having crossed that hurdle, she doesn't mind that she has to speak aloud in front of Sherlock to find what she's looking for.