The only way I can see a 4.5 taking games/set/match/whatever off a "pro female" is if they can just manhandle the girl. That's the only way I can take games off the college girls that I know. They're not exactly 5.5's, but I can see it scaling the same way.
You are not going to junk ball them, out consistency them, or out fitness them. That I know for sure. lol.
If you want to have any chance at all, you're going to have to basically manhandle them and beat them with pure power and getting the "good end" of the statistics more often than not.
You're going to need aces.
You're going to have to force bad returns.
You're going to have to blast winners off their serve.
You're going to have to pass them if they come in.
You're going to have to pound corners hard, very hard.
There is no way I can see a 4.5 winning against a pro lady any other way besides raw power and "risky" placement and shot selection.
"In the 1980's two men dominated--sometimes each other, most of the time everyone else."