My LO will be 20-21 months when new baby comes along.
What can I expect with her?
Will she still be napping during the day?
Sleeping better at night (not waking at 5am?)
Still n a cot or her toddler bed?
Will she be able to talk/understand?
Anything else I should know?
This depends on the child, but I have my own 19 month old and I am a childminder so have a 22 month old (soon to be 23 months) during the day Mon-Fri. Both children still nap about 2 hours during the day - they are put down and go to sleep within 10 minutes and sleep well. I can't speak for the 22 month old as she doesn't sleep here overnight and she is brought to me for 7am so is woken up at 630 whether she wants to or not, but my own daughter has slept roughly 12 hours overnight for months. She's gone to bed at around 7pm since she was 4-5 months old, and gradually stretched out her wake-up time; in summer it's a bit earlier but since the dark nights have come, she will easily go til 7am or maybe later.
My daughter and the minded child are both still in cot beds - I know my daughter and don't feel she'd settle in a bed at the moment; she will go into a bed in the new year, though.
The speech thing depends on your child - they all progress at their own rate. My minded child is fairly advanced and says 4-5 word sentences, can repeat any word and know its meaning rather quickly, has a LOT of words in her vocabulary already. Her speech isn't clear but she can be understood. My daughter is about 4 months younger and has lots of words, a few two word sentences, babbles a lot, uses a lot of conversation skills when she babbles, but she's not into the 4-5 word sentences or anything yet. She can be easily understood through the words she does use and the gesturing she uses, so I think your daughter will be able to communicate by the time baby comes along.
Both the girls love playing with teddies and dolls (but will play with most toys); both girls have increasing attention spans, will listen more to books, watch a small amount of tv (I only allow a small bit when oldest mindee is here as he watches it - he is 5), listen to instructions and understand what is said to them, understand the word 'no' and usually adhere to it. They are both starting to enjoy craft activities more and have more of an attention span for things like colouring/scribbling. They both feed themselves (make a bit of mess, but my daughter has always fed herself as I did BLW); they both eat most of what's put in front of them. They help tidy up (and understand when I say it's tidy up time). They both have cows' milk in a beaker a couple of times a day, water the rest of the time.
Neither of the girls are toilet trained but the 22 month old is very very close. She can control her bladder (pulled her nappy off during a nap the other day and both bed and nappy were dry 2 hours later), knows when she's wet or pooed, knows names for toilet activity, asks for nappy to be changed. So I think around 2 years old will be good for the potty training.
Both girls can walk quite a long way (my daughter can walk further than the 22 month old - she has far more stamina but she is used to walking). It is difficult to stop one or other of them running off as they have no sense of danger yet, so a double buggy is a necessity.
Good luck.x