I am just saying that if you get another horse they will deserve equal attention unless they can only function as a companion.
Another thought I just had, that helped me with figuring that^ out last summer, was fostering a rescue horse for a local horse rescue.
Last summer I decided to foster a horse, thinking that having another horse was a logical 'next step' for myself. Someone on HF suggested fostering to me, I looked into it, and within a few weeks I had another horse to take care of.
And boy, that was a huge wake up call. I've done plenty of work with herds of horses but never just two horses and never with my personal mare in the mix. I also realized that if I were going to get another horse, I had very specific training+temperament requirements. I had thought that pretty much any horse in need could cut it = NO.
I ended up spending a whole lot more time dealing with the shenanigans of this foster mare, training the foster mare to a point where she was less likely to kill someone just by being a dork, working the foster mare so wasn't going nuts from energy build-up... It was just way more time and energy than I had had any idea of and way more work than I really needed. Not to mention that my mare was constantly stressed by the really high excitement level of the foster.
I think, out of the seven days in each week, I spent time with my mare exclusively MAYBE once a week. The rest of the time I was using my mare to pony the foster, or doing other activities with the foster. Because my mare wasn't an issue, she really got the short end of the attention stick while I tried to put out the 'fire' that was the foster. The foster was a super sweet, great, horse and in any other context I would have LOVED her...but she was just not right for my situation or my mare.
I feel good about helping that mare on her journey towards finding her forever home BUT I'm glad I didn't get another permanent horse. The goats are much better in terms of energy levels, training requirements, etc, and I never would have even considered goats if I hadn't done the foster thing first.
Anyway, fostering might be something to consider. Many rescues have 'pasture pal'-type horses available to foster homes. That might be a good way to dip your toes in "the water," find out if another horse would be the right move, and maybe you'll even find your horse's perfect companion!