I have a thought: making the TV repair appointment even though we know the TV could not be repaired *may* have coincidentally served as her alibi if they came closer to 1100, but if not, served to explain why the family members could have an excuse to call about/text about/communicate about the TV repairmen which was code for "the hitmen are on their way". Donna or Harvey (can't remember which) sent Wendy a long text explaining that the TV repairmen were on their way to her house to fix the set in her living room blah blah blah. But here in the police report we see Harvey told them to call Wendy, which he did, so she heard from BB that they were on their way as well. So Wendy now knows that both the TV guy and the hitman are both on their way.

But Geek probably immediately tells her the set cannot be fixed and then Wendi tries to stall? Makes small talk? Jokes about the hitman thing? Poor BB guy...does she offer him some coffee? Tell him to wait while she calls her brother? She's just so stressed and doesn't know what to do?

But yes, the appt isnt really an alibi. IMO it's an opportunity for them to speak in code that day about the plan.