I am with Norrington, who’s also dating Elberta. This is my first poly relationship. On my birthday, Norrington mentioned that Elberta helped him choose a lovely, thoughtful present for me. Elberta and I get along, but aren’t very close. I’m not sure how to feel about her apparent involvement in mine and Norrington’s relationship, but I also know she meant well - she was being kind and helpful, not jealous or invasive (I don’t think). So my question: is it normal for metamours to be a little bit involved with the other’s relationship?
Yes, it is normal! Usually, people tend to have ‘types,’ or general personality preferences, when they date, so metamours often have certain things in common. So Elberta would likely be a good resource for Norrington to ask “what kind of gift should I get someone I’m dating? Do you think my other partner would like this?” And since the gift was, as you say, lovely and thoughtful, it sounds like his instincts were correct!
We use the word “partner” for a reason - because relationships are partnerships. People do things with their partners and often seek help, advice, support, or collaboration. Norrington is dating Elberta presumably because he thinks she’s intelligent and he respects her perspective. So it would make sense for him to consult her on this! Since she helped him choose something nice, she clearly was not acting out of any malice, and only a desire to help out her partner and metamour.
And even if it wasn’t “normal,” that wouldn’t necessarily make it problematic or bad. You got a great present, you have a metamour who supports your partner in his relationship with you, it’s all working, if it ain’t broke, don’t fix it. So if your question is genuinely “should I feel uncomfortable with this?” then my answer is a resounding no.
But if your question is really “I feel a little weird about this, and is that okay?” then my answer is a bit different. Of course you can’t control your feelings, and sometimes things bring up feelings for us that don’t feel useful or fair. It might help to think about why you feel uncomfortable. Do you feel like the gift isn’t really from your partner, and you wish he had done all the effort to figure it out? Do you just not like the idea of his other partner being involved? Do you feel pressure to get closer to Elberta, but you aren’t interested? Press in a bit on that discomfort and identify what’s going on with you so you can talk with Norrington about it and have a clearer problem/solution in mind besides “idk about her involvement in this.”