Hi there, hope you don't mind me jumping in

I noticed this:
we had a decent routine of her being put down for a nap after about 1:40 of A time, with her being asleep 20 minutes later.
which adds up to a full 2hr A time when you last had some more reliable naps (however, still short it seems with being 45min-1hr 15) to me it indicates your LO is really for a significantly longer A time. As she is 5.5 months and ever growing I'd look to increase to 2hr 30 immediately with a view to possibly increasing again to 3hrs over the next 2-4 weeks. Adding just a few mins A at this age is not going to help IMO (ie extending to 2hr 5 mins isn't going to help). Some LOs this age already need 3hrs.
I would also Go in at around 30/40 mins and ready yourself to help her through the transition into the next sleep cycle, if she has habitually slept 45 mins, one cycle, over the past months she may not yet have learned to transition. This is something you can encourage and 'teach' through helping her know when she is supposed to stay asleep and when it is time to wake up.
WRT worrying she will get OT from A time increase. Try not to worry, so many people do, the thing is if she gets a bit OT it will help her sleep in the end, it is just as hard (harder in my opinion) to deal with a baby who is UT and short napping through not being tired enough. Looking at your days there are some very very long A times thrown in there where she's either refused a nap or whatever reason, increasing A times is not worse than this but in all likely hood is going to lead to longer naps and help to avoid those really long A times happening.