IIRC she’s previously stated that Article 50 is going to be invoked in March.
This speech isn’t a declaration of Article 50. It signals that May’s cabinet has been clearing blockers and successfully reaching out to new trade partners.
The agreement will have to go to Parliament for a final vote because of Constitutional requirements that rights can only be removed by a positive action of Parliament - e.g. a vote. It’s not her choice: that particular spoke was introduced by the Europhile UK Courts.
Time for you lot to have yourselves a tea party....