There is a chance of waking and crying being UT too - I know we usually say OT but you also need to look at the A times and what the history of A times tells us too. I have definitely experienced my DS waking crying when UT and I had many people advising to reduce A time but he had been doing longer happily prior to the problem...then one person suggested UT and I increased and it made him tired enough to transition which meant he slept longer and was happy again. So I think you are thinking on the right tracks of increasing to 3hr 40 but you might need ot help her, I'd go in and start W2S before she wakes so that she isn't screaming and try to catch her in the drowsy stage and rub, pat, stroke, or jiggle in the cot and use shush or key phrase to get her back off if possible.
Of course it could be the other way around and it could be OT but based on what youv'e said I get the idea of UT and just needs help to adapt.
Dashing out on the school pick up now but if any of this isn't clear let me know i'll try to get back later.