he's a teenager. we all know he can probably sleep anywhere!!
have him get up with her and take her potty, then he can crawl right back into bed and get a few more minutes of sleep.
then the next day, have him wait 5more minutes. eventually she'll be able to wait until he rolls out of bed just in time to make the bus after taking her out
she will be able to wait and is just a baby right now.
hopefully your son will think this is a brillant idea ...