Gift with reservation and spouse exemption

I am dealing with an estate where Husband set up a flexible life interest trust in 2001 where he was the life tenant. Following Husband’s death in 2022, the trust income is due to Husband’s widow for her life. Will the fact that the widow has a life interest in the trust fund under the original terms of the settlement mean that spouse exemption will apply to the settled property which is subject to a reservation?