Those are some big cacti if they managed to "bury" her.

There are Cacti that can reach heights tall enough for the average Transformer. The Saguaro cacti can grow over 40 ft (12 m), with the tallest having been 78 ft (23.8 m). The Mexican giant cardon cacti on average grows to 30 ft (9 m), and tall ones reaching heights over 60 ft (18 m) with some weighing around 25 tons. Such plants though would be quite old, as they're rather slow growing.