I always feel she plays better against better opponents, but when playing lower ranked players her standard drops. No concrete facts to back this up though.
I can't quantify her standard of play, but in terms of results in the last 52 weeks Heather has won 43% of her matches against players ranked higher than her (10-13) and 70% of matches against players ranked lower than her (21-9).
In those matches against players ranked lower than her, she is 11-3 against top 200 players and 10-6 against players outside the top 200. Drilling into that further, she seems to struggle particularly against players ranked 200 to 300 where she is 3-6 in the last 52 weeks. Perhaps, also worth noting that the 2 players she has played outside the top 500 in the last 52 weeks, she lost the 1st set on a tie break before going on to win the match.
So perhaps her results do provide some support to your thoughts.
A few too many DFs including one by Olivia at *7-5 up in the MTB. That was immediately followed by a jammy net chord to make it 7-7*. Saved one MP at *7-9 but not the second.
Just saw most of the second set TB and MTB (.well until 8- 9* when bet365 cut out so I missed the final point ) but the girls were certainly looking feisty and competitive against strong opposition.