Hi,
You can contest her claim and it will go to a Land Registry Tribunal, where a judge will here both sides of your stories and decide who he believes, like what happened to me.
After that if he believes her side he could judgde on a percentage share shd should get or advice for both parties to agree.
If no kids involved and she wins the case you can go to court to force a house sale or buy her out.
I ended up with a
Consent Order which we agreed a percentage each when house gets sold when our son is 18, she can live in house but pays mortgage until then.