The C_A has many jobs requiring many skill sets. They recruit people with different backgrounds, but linguistics is a really good way to move up the line in getting a job there. Russian speakers were useful for many things - translators, radio intercept officers, OC and NOC positions. Back in the day, radio operators who were hams were recruited and had to pass a Morse Code proficiency test in addition to a lot of written exams and deep background check.
Nellie's ham license is too recent. I had asked an anon who lives near her to find pictures of her house to see what kind of antennas she had. I was trying to understand if she had HF radio gear and was thus able to use it to talk overseas.
This would enable her to speak with Steele as I believe he also speaks Russian. Certainly MI6 has Russian speakers.
At present, we have surmised that she's used DMR radios in the 2m/440 ham bands. What we don't know is about HF.
I hear Russian on the ham bands infrequently, but it is there. Most hams - even foreign hams, speak some English. Most of our Morse is in English.
Perhaps Q could drop us a crumb to know if she was subject to a HF intercept. That would really expand our thinking.