I’ve had similar frustrations with Duolingo - and I’m not even as far along with it as you are, @hewrop, because it hasn’t given me gwelais or ffrind yet.
For anyone else using Duolingo: never forget that Duolingo isn’t a human teacher, and isn’t capable of saying “You know, come to think of it, you’re right! I hadn’t thought of that way of saying it!” when you give it a different answer from what it was expecting.
It’s a computer program, comparing each response you provide to a fixed set of responses that it has stored in its database - and whoever compiled that set of responses hasn’t necessarily thought of every possible way of saying it. Even if the set has been added to over time by other people, there’s no guarantee you couldn’t think of still more variations.
The right/wrong test is very binary. If your response exactly matches one of the responses in its set (ignoring case, and ignoring punctuation marks external to words), then it assesses you as correct.
If not, it drops through to the next test: is your response only one letter different, or maybe two? (I haven’t tested it to see what the limit is.) If so, then you’re correct, but it will warn you that you made a typo. Sometimes I really have forgotten the Welsh word, but because my misremembered guess is only one letter different, Duolingo treats it as a typo. Its algorithm can’t tell the difference between a typo and genuinely not knowing the answer.
But if your response doesn’t fall into either of those categories, then Duolingo will say you’re wrong. It doesn’t matter how right you are in real life - as in the “a friend of Megan” example. Duolingo is a computer program with a fairly simple algorithm, and is just not capable of assessing the rightness of an answer beyond that algorithm. It requires a human to make that judgement call, and that’s why Duolingo has the reporting mechanism.
I agree it’s immensely frustrating to be forced to retype an answer when you are sure that what you provided was correct. But until they act on your report and add your suggested response to their database of correct responses, that’s all you can do. Personally, I just swear a bit, then shrug, type whatever Duolingo wants, and move on.
Your post does illustrate the value of finding a human conversational partner! The most sophisticated automated program will have some way to go before it can match a real, live, fluent Welsh speaker.