I stayed in both two weeks ago (2 nights at Swan, 4 nights at Dolphin) both in a King standard room. Both are a good location for Yacht Club, I walked over there a couple times. Also if she is a Marriott member she'll receive points/benefits based on status, of if you have Amex Platinum or Gold they are part of "The Hotel Collection".
My observations:
- Swan is a smaller hotel in general, less of a lobby, a few outdoor interior areas to sit in but not much open space.
- Lines at the Swan for the quick serve breakfast place seemed shorter.
- Dolphin has a big lobby and more rooms in general - there were also a lot of unmasked people around and the indoor masking policy was not enforced - that may or may not matter to her
- My King rooms at both had sofas. The Swan room had an ottoman - may just have been luck. Room size felt the same to me and was typical for a business hotel.
- Bathroom at Swan was a slightly better layout with 2 sinks - but both had a separate shower/toilet room - not a big deal for a solo traveler.
- With my platinum card upgrade I got a balcony room at Swan, but no balcony at Dolphin - again could be luck
- My Dolphin room had a fireworks view from the couch, Swan does not face Epcot.
-Walk is slightly shorter to YC from Dolphin, but not enough to make a difference.
-Swan is Westin, Dolphin is Sheraton - Westin is a higher brand, if she's a Marriott loyalist you can tell the slight difference.
Swan is usually slightly more expensive, it was only $20 for me. At the same price I'd probably go with Swan, unless I knew I could get that fireworks view at Dolphin bc that was nice some nights.