Why did Lisa Cameron defect to the Tories?

Lisa Cameron, the SNP MP for East Kilbride, Strathaven and Lesmahagow, defected to the Tories last Thursday.

It's a headscratcher. If she believes in independence, why not defect to the Greens or Alba? And given everyone thinks the next election is in the bag for Labour, why not defect to them?

Here is how East Kilbride, Strathaven and Lesmahagow voted in the 2019 election:

SNP 46.4%
Labour 22.7%
Conservatives 21.2%
LibDems 6.7%
Greens 2%
UKIP 1%

The SNP gained the seat from Labour in 2015 (Labour used to win the seat with about 48% to 51% before their vote migrated to the SNP after the Indy Ref).

It looks like she was motivated by her disapproval of the SNP's self-id gender policy. Labour's policy on this is the same as the SNP's, though Starmer has taken to waffling uncomfortably when asked about it.

The Conservatives are not only against self-id, Rishi Sunak triggered Section 35 to block the SNP's legislation in Scotland.

So it looks like a defection based on principle. But how many of her constituents agree with her? We shall find out at the next election.