Hi & welcome Kona,
Yes, horses are herd animals, so it's great that your mare is no longer alone. As with any new group of animals(or horses separated & reintroduced) there are 'politics' while they sort out their relationships. Horses are pretty peaceful animals & tend to settle down quickly, *if they're allowed - see above. Sometimes you can have the odd 'bully' that keeps it up or is unnecessarily 'bossy', but mostly...
So, if your mare is used to being with other horses previously(those that have been kept socially isolated often don't know how to be reasonable), and this 'subservient' gelding heeds her 'bossiness', they'll settle into their spots without much issue.
The problem is, that may mean that one gelding may be told to keep away from you - in her eyes, you belong to her, she doesn't want to share with him. So I handle this by assuming leadership whenever I'm in the paddock, and the 'manners' I expect include no horsey politics while I'm in the vacinity. I will strongly drive off or otherwise punish any horse for 'telling off' another, whether that's reasonable in-herd behaviour or not. I can go into the paddock of 10 horses with a bucket of feed(most aren't mine so only get a small taste, if that) and safely feed my horses & ask them to take it in turns from one bucket(they only need it for supps).
Funny, cos the 'bully' of the herd, who's just dying to drive everyone away, usually hangs back & looks confused - he doesn't seem to know what to do if it's not hassling someone. He's a very friendly, 'in your face' horse whenever he's allowed & he waits for me to come to him & offer him a taste.