Robert Todd Lincoln --The vitals

[Eva Elisabeth]

A lot of people who knew her in person liked her (and kids in general it was said). I think those people were able to understand she had a good, warm, loving and giving side (which I think she had) despite her tempers. Maybe Mr. Burlingame would have changed his mind had he met her in person. Maybe not, she possibly just doesn't match HIS idea of a "suitable" wife (for him or in his world view... same goes for Hendon). And none of the critics seem to acknowledge she was capable of "dealing" with Abraham Lincoln, his needs in life (career and resulting absence etc.), his moods etc, his "non-etiquette" behavior, his challenge seeking mind.
As for she (or he) and affairs, I think she was faithful as was he. However, until a "love letter" pops up that clearly proves anything else this will always remain a matter of belief gossip and speculation either way. Mary never re-married nor had an affair after his dead when it would have been legitimate, most likely accepted by many, and not unusual. My best guess is that she tried to "let her southern belle charme" help her getting out of debts (without going any further than entertaining conversation, charming small talk, the Scarlett O'Hara way).