A rheo/dimmer is a short-term solution since it takes time to order a decent t-stat and get it shipped - or in the OP's case, she needs some time to save up or to get her next paycheck so she can buy the t-stat.
As was pointed out, if your room's ambient temperature fluctuates then the pad will fluctuate also, as the rheo/dimmer won't adjust the pad to keep it the same temp no matter what the room does. So, if the pad is 90*F with a room ambient of 75*F, then the pad will go to the mid-90's if the room goes to the mid-70's.
And yes, since some t-stats fail wide open - I found out recently that VE's do, more's the pity since a lot of people use them - then it's not a bad idea to install a dimmer between the t-stat and the heat appliance so that if the t-stat does fail the heat won't go so high that your snake ends up burned or dead.