Venus won their only previous meeting. That was in Charleston in April 2016, clay. She won in straight sets on clay.
Riske has ridden her luck a little this week. She needed 3 sets in her opening 2 matches. She lost the opening set in both and was pre match favourite each time. Vandeweghe retired from their quarter final early in the 2nd set.
Venus improved in her last match from her opening one. She gave far fewer chances to Bellis than she had to Linette. If she maintains that level today she wins.
I expect the sets to be close and will back Venus if she goes a break of serve behind.