These moments are always very difficult. I am sorry, you have to deal with them now.
Give yourself time to decide.
With your neighbor’s horses, I would agree with GFAG, it might be enough, once your mare comes to terms with her new situation.
If not, you can do a short term board with your trainer, which can “buy” you more time to think about, whether you want another animal and the life that comes with keeping horses at home.
Of course, there is nothing wrong with bringing “a new kid on the block” soon. We will enable you the best we know how. :yes:
My friend lost an animal short time ago and, a couple of days later, another one arrived. Through the equestrian grape vine, it became immediately known, there was an opening in the pasture. One of her friends called with this I-am-sorry-and-here-I-know-this-animal-do-you-want-him and that was it.
I know, however, this person wants the lifestyle 100%, hence her quick decision.
Anyway, I would be surprised, if your friends did not start to alert you about new candidates soon.
Naturally, my ideas generally revolve around minis. So, I would recommend a mini horse or donkey any time. Nobody knows better, how to mend a broken heart than a little fuzzy ball commanded by a willful, mischievous brain.
ETA: Personally, I am firmly in a camp two is a minimum, three is better (for small backyard place). A mini counts as one. I do understand, it is not always an option.