I'd just make sure to give your senior dog plenty of attention with the puppy in a crate or somewhere out of the way. I have a 12 yr. old Beagle and Alice (7 months) likes to jump all over her, lick her face etc. I don't have the same issue as you because it's actually somewhat brought out the "puppy" in my old girl, but every dog is different. My old dog will let Alice know when enough is enough though
.
When I give the other two dogs their individual attention each day, Alice tries to intrude and I just don't let her, she has plenty of her own time with me. Of course there's times when I'll play with all 3 of them together, but it's important that your senior dog have her time too and not feel like she's been replaced with your affection.
She's probably just annoyed by the puppy's energy and that's why she stays away. I'd also figure out a way for the older dog to have a way to "escape" the puppy whenever she wants - somewhere she can eat and lay down comfortably where the pup can't or isn't allowed bother her. Maybe buy her a nice new bed or something like that. Let her go outside by herself at least half the time too.
Honestly, when they get that old, I'll pretty much let them have whatever they want lol. I have zero problems ever with my beagle eating lol, but if she didn't want her dog food that day, I would boil her some chicken or give her some treats - whatever. I kind of throw some "rules" out the window a bit when they get to senior status and pamper her a bit more
.