We're already planning on eating at Ariel's Grotto and Blue Bayou. I'm glad there are nice views at both. Do the princesses come outside to the patio tables at Ariel's?
DM does not like to stand in line for food - counter service really isn't an option.
How difficult is it to get the outdoor patio tables with views at Carthay Circle or Wine Country Trattoria? Looking at menus, I think those are the ones most likely to appeal to her that we haven't already booked.
WCT has plenty of outdoor seating, That was where we were seated, on the patio, it was really nice.

I don't know about Carthay, we have been seated inside while dining there.
Yes, the Princesses come around to all tables, inside and out.
For the best view at BB ask for waterside seating, you may be told it will be a very long wait but it really shouldn't be too bad at all.
When requesting certain types of seating you do need to make that request at the restaurant when checking in, they may make a note when you mention it while calling but IME it is rare that they do so. I've had better luck simply asking upon check in.
I believe the princesses only are guaranteed to come around during the character breakfast at Ariel's. I don't see why they wouldn't make their way outside. One time we got lucky as we were sitting outside for lunch. The princesses, Jasmin, Cinderella, and a couple others came by and signed my cast! I think this is rare though.
I don't think it's that difficult to get a table with a good view at CC or WCT, but you might have to wait longer . I would call ahead to make the reservation (instead of making it online) and requesting a view table and also mention it to the host when you check in.
The Princesses at AG come around for breakfast and lunch, dinner there is WoC dining and instead of Princesses you get priority fastpasses to see the show. The Princesses always come visit diners seated on the patio as well, it is not rare at all. We used to ask to sit outside in nicer weather as the prices were a bit less, I'm not sure if that is still the case or not though. We also asked to sit there because those were open tables and not reserved so we could be seated faster.
Personally my two favorite views in DLR are at CS places, not TS, RiverBelle Terrace where you can see the Rivers of America and Hungry Bear where you can also see the Rivers, I prefer the lower level of the HB and I try to sit in the back, I've seen many interesting things back in that corner.

Of course BB is amazing, I love the bayou itself.