Hi there,
My DP is Spanish and would say she was fluent in English (very good English accent and only noticeable she is foreign when she pronounces certain words, but you couldn't guess she was Spanish at all) but when she gets angry/is tired tends to switch to Spanish. We have been together for 7 years now and it has always been like this, although we did spend the first 4 years of our relationship mainly speaking in Spanish, whereas now we mainly speak English. I do have have a degree in Spanish but feel our relationship works better in English. AIBU thinking English will never become totally natural for her? Would be very interested in hearing the opinions of any foreign ladies who have an English DP.