I would start off with how you still regret not being able to make it to the funeral (if you do) i would then go on to inform her about your recent life, maybe enquire about hers, i would write stuff that a reply isn't necessary to, so less questions more information, maybe say i hope you're doing well kind if thing.. I'd more update her of your life, say merry christmas happy new year, hoping it brings more positivity. Let her know you're there if need be etc..
Dont say anything forced, and try not to force a reply. Keep it laid back, especially if she is still in heavy morning over her husband (which i imagine she is ) Try not to dwell in any negativity so when she reads the message, it's more positive than melancholy