The 29-year-old Guernsey player spent her younger years growing up with Tara Moore and overcame her friend 6-3 4-6 6-2 to register a first WTA Tour win since February.
The British number two had not won since the opening round of the Australian Open but put some building blocks in place for a British summer that culminates at Wimbledon.
'Tara, I have known her pretty much my whole tennis life, we are the same age and we were the top of the age group so we have gone away and played team events together since we were like nine,' Watson said.
'Then we both moved out to Florida together and went to school there at 12, so I have known her forever.
'She is a great player and I knew that it would be hard today, but I don’t think I have played her in about 10 years, though.
'I haven’t had the best of years but I am really happy to get through today because every match I get over the line it gives me a lot of confidence.'
On Thursday’s last-16 match-up with Katie Boulter, she added: 'I know her well, we play the Fed Cup together. She is a good player, so it will be really tough. I have got to recover straight away and do some homework.'