Without a heartbeat or a pulse, she won't feel the same awful your-blood-is-pumping wrong feeling, and will be able to withstand the tunnel for longer than most because of it! After a while (think about double the time of normal folks with functioning hearts and blood), she'll start to get an absolutely piercing headache and feel her head throbbing in time with the pounding rhythm. Her thoughts will also start to race in a way that makes her dizzy.