She would need the backing of both the European Council and the European Parliament to get a third term. That is extremely unlikely to happen. Moreover, the European Parliament can kick her out at any point if it really wants to.

There are also hard limits on what she can do as president. Brussels doesn't rule over the member states like Beijing rules over the provinces (Chinese + "acquired" ones). Most things need the backing of the Council (= the member states) + the member states can drag things out at home if they want to. The EU doesn't have anything like the US National Guard that can be used in member states to force them to comply (possibly against state laws and state constitutions).

The European Union is the consensus making cooperation machine many European countries have chosen to use and die Uschi is only in charge of one component of that machine.

Doesn't seem very rulery to me.