Certainly she should have a lofty advantage in grappling but I'd like to see more aggression from McMann in this fight, more damaging ground and pound. Fact is, she hasn't finished anyone who's any good yet and didn't convincingly beat Baszler (like Davis did).
On paper, Gaff and Sexton have both been brought in as cannon fodder. A lot of people underestimated Zingano against the more well-known and hyped Tate and we saw how that played out.
If Sara fights smart (i.e. GSP vs Diaz) she should dominate with take downs and top control. If it decends into a tear-up (like the last few seconds of McMann/Baszler), I fear Sheila will connect first... and swarm.