root, custom rom and kernel and overclock
this will at least improve the situation until there are more selections for phones that meet your criteria
For starters, I never knew anything about the Merge until s44 mentioned it. So it goes without saying that there's stuff out there that someone other than myself might know about. Second, I'm not up to snuff on the particulars of all the phones that are currently available, which is why I through out specifications and people with experience correlate and itemize phones that have and don't have features I'm looking for.
I'm not going to find out if I don't ask, right?
To answer your edit - no, I want to get her a new phone, something different and somewhat less flaky than the one she has. Experience dictates that it not be a Droid, since between her wants and experience, the Droid isn't what she wants nor what I want to support.
I hear you.
But how is a Droid-branded phone any different from a different Android phone? They run the same OS. If her Droid is "flaky," then either there's an actual hardware issue (in which case a new phone of any kind would fix it), or there's a problem with the Android OS (in which case, no other Android phone would be any different), or it's user error (in which case, nothing can really be done about it). That's why some suggested doing a complete wipe and reset of the phone. Unless you're messing with roms and stuff on a regular basis, or downloading bad apps, I don't think there's any reason it should get progressively slower with time.
Droids are no different from other Android phones; they're not even all made by the same company. Some are Motorola, some are HTC. It's just a brand name Verizon uses.