It is often difficult for third parties to know if a spousal couple has “legally” separated or not and a sudden death will invariably lead to litigation over the issue.
The Courts have established in Manitoba, and I believe it would be followed in BC, that in order for separation to be established “the evidence of separation must be “clear and convincing”, and the intention to separate must be “communicated to the other party and acted upon”.
Venditti v. Slobodiianik 2013 MBQB 202 has the following quote of law:
23 The cases of separate and apart under the same roof generally focus on the physical living arrangements of the parties but there is another important consideration as well, namely, whether one or both had formed the intention to live separate and apart thereby destroying the consortium of the married relationship: see apart thereby destroying the consortium of the married relationship: see Eamer v. Eamer (1971), 21 D.L.R. (3d) 18 (Man. Q.B.); Herman v. Herman (1969), 3 D.L.R. (3d) 551 (N.S.S.C.); Coates v. Coates,  M.J. No. 272, 146 Man.R. (2d) 249 (Master Harrison – Man. Q.B.) – upheld on appeal 2000 MBQB 197.
24 As well, Molodowich v. Penttinen (1980), 17 R.F.L. (2d) 376 (Ont. Dist. Ct.), a unmarried cohabitation case developed a useful list of factors and components deserving of consideration when courts are called upon to consider when “unmarried cohabitation” begins and ends. In doing so, Kurisko D.C.J. reviewed many of the historical decisions on marriage, consortium, conjugal relations and cohabitation. The Molodowich list of factors has been commented on favourably by the Supreme Court of Canada in M. v. H.,  2 S.C.R. 3, and has been used and applied in a number of cases in Manitoba and elsewhere. In Manitoba see Huberdeau v. Reid, 2007 MBQB 69; McGee v. Ranson, 2003 MBQB 182; Maresich v. Penner, 2007 MBQB 85; Bullied v. Kallen, 2008 MBQB 268.
25 Two further cases provide helpful reference points and hearken back to the injunction in Galbraith, supra, that the evidence in support of a claim of separation or cessation of cohabitation must be “clear and convincing”. In Gibbons v. Kowal, 2006 MBQB 11, Hanssen J. held that:
A conjugal relationship ends “… when either party regards it as being at an end and, by his or her conduct, [demonstrates] in a convincing manner that this particular state of mind is a settled one.” [para. 9]
26 Finally, in Field v. McLaren, 2009 MBQB 118, Douglas J. (as she then was) in the context of a common-law partner Family Property Act claim held at para. 10 that:
Certainly I accept it is settled law that the intention of one party to separate may be sufficient to sever the relationship. Judged objectively though there must be evidence that an intention to separate was not only held, but was communicated to the other party and acted upon. The person desiring to separate must act in a way consistent with an intention to separate.
. . .
48 A discordant and disrupted marriage over many years is not the equivalent of a separation or cessation of cohabitation.
37 In summary: cohabitation may be considered to continue notwithstanding a “discordant relationship”, the evidence of separation must be “clear and convincing”, and the intention to separate must be “communicated to the other party and acted upon”.