I agree that the transition for the whole family when a new baby is born is massive and takes time. We had a similiar age gap and I was shocked at how my nice little girl turned into a horror almost instantly. To be fair she was the centre of attention for everyone up until that point and then no one paid her too much attention at the time the baby was born. Add this to sleep deprivation and general 2yo stuff and it was not pretty. I had some advice to point out to her that we were having mummy and Zoe time when we went to bed and then do the same when she was having one on one time so she actually realised it.
I often look back on that time and feel like I hardly saw the baby - she woke, fed and got plonked back down. Luckily she knew no better! I think you just need to be kind to yourselves and give it some time. If you really feel she needs to be checked out then perhaps ask your MCHN her opinion. I would not worry too much about other people tho - it is a big change and often people who are not used to little kids forget how normal meltdowns etc can be. Do you have outside stuff you can do without going anywhere? Sand pit, water table, trampoline? I found being outside much better at expending energy and we blew and chased LOTS of bubbles in the early days between feeds. xxxxxx