Frilford Heath member Katherine O'Connor recovered from six shots behind to win the Welsh Girls strokeplay event at Woodlake Park.
The 17-year-old was six shots back after the first round, but a level par score in the afternoon saw her roar back and claim the trophy.
O'Connor then won the first round of the championship matchplay event before losing out to Vale of Glamorgan's Anna Carling on the final hole of their quarter- final.
Her performance, however, earned her selection to the Welsh Girls team for the Home Internationals at Southerndown, which began yesterday.
This call-up means O'Connor is unavailable to play for Oxfordshire in Junior County Week South East Division 1 at Hadden Hill.
Oxon's squad for the event, which starts on Monday, includes Laura Watkins (Bicester), Claire Reynolds (Chipping Norton), Flora McPhail, Nicole DuPlessis and Sophie Purcell-Smith (Frilford Heath).
Abi Laker (Burford), Gemma Clements (Studley Wood), Natalie James (The Springs) and captain Lauren Jupp, from Studley Wood, complete the line-up.
Oxon take on Berkshire, Buckinghamshire, Hampshire and Hertfordshire.
- Eddie Pepperell, 16, from Abingdon, has this week been representing England in the Boys Home Internationals at Machnynys Peninsula in Wales.
- Banbury's Gary Boyd, who plays at Cherwell Edge, was a shock first-round casualty in the English Amateur Championship at Royal St Georges.
The 20-year-old equalled the course record at Royal Cinque Ports with a 64 in qualifying, but then lost out to Michael Moore at the 19th hole.
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