New companion suggestions

I have a 3 and 1/2 year old Holland Lop named Mystery. She originally had an older sister named Lily, who has sadly passed away a little more than a week ago. I'm worried that Mystery may be lonely and may need a new companion. I was curious to know if anyone had any kind of suggestions on what kind of companion would be best for her. She is not fixed, and she is always been kind of grumpy, but she always cuddled and played with Lily. I just don't want her to be lonely.
If anyone could help out that would be really appreciated.

This is Mystery.

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Mystery is so cute! Maybe try bunny dating at a shelter?
I would just suggest a neutered male, other than that I have nothing. Picking a bunny is easier than deciding how you want to bond them, good luck!

Definitely get her spayed before any introductions. Introducing two adult rabbits when one isn't altered is a recipe for disaster, as their hormones are much too strong. Females are often territorial and aggressive toward new bunnies.

Get her spayed first. Not only is it almost impossible to get unfixed adult rabbits to get along, but your bunny is at the age when she will get uterine / ovarian cancer if you don't do it very soon (the risks are over 80%). Once that's done, you can think about getting a neutered male to keep her company (don't attempt it with another female - it's a lot more difficult to bond than a male / female pairing). Give Mystery a chance to live a long and healthy life before thinking about how lonely she may be.

We plan on getting her fixed soon.
Should I find her a partner around the same age? And would the breed matter?

OK, that's good ^^.
No, the age doesn't really matter except that you won't be able to put the two of them together before they are both neutered / spayed so it's advisable to take a neutered male (so over 4 months). I did the 'take a baby, keep them separated until the hormones have died down after the neuter (around 6 weeks after the operation) and then put them together' before and I wouldn't do it again. Like never. With a (spayed!) female in the house, the hormonal stage of the baby was the worst (think urine sprayed on your walls and furniture, biting, the baby doing everything he can to escape his pen... the extra pen taking half of a room...) and I could have married the vet who finally neutered him because after a few weeks I felt like throwing the little monster out of the window.
Rabbits have always been bred for their fur, not their character so no, breeds don't matter at all except when it comes to the owner's personal taste. I have a Nethie and a dwarf lop and they get on great. I know people who have a Netherland dwarf and a Continental giant together and it's no problem at all (actually, my Nethie is half the size of the lop and she's always been the boss).