I’m so sorry, HT! How recently did your other bunny pass? I know this sounds weird, but did your surviving bunny get to see the body? (Oddly this can help them cope because then they know what happened, so if she didn’t others might have ideas about how to help respond to that situation.)
I’ve only had one pair of bunnies so I don’t have that much experience, but I’d suggest you just spend some quiet time nearby, only as close as she’s comfortable with. She might be feeling uncertainty as to what’s going on, and grief for her partner too, but she’d probably enjoy some gentle companionship. So maybe just bring a book or laptop or whatever and sit on the floor a little ways away. Maybe offer her some healthy treats like herbs or whatever she likes. If she’s afraid of being petted, give that a rest for a little bit. She probably needs some time to grieve and to adjust.
I’m guessing she’s also pretty young, so she might benefit from another companion at some point soon, but it’s probably a good idea if she has time to go through the grieving process first. Bunnies develop very specific/personal relationships so she needs a little time before she’s ready for a new companion, kind of like humans do.
My advice should be superseded by any moderator or other person with more experience, but I wanted to offer some ideas for now. Sympathies to you and your bunny!