New Baby and 2 Yr Old Sleeping

my daughter(3) did the same thing when i had my son(now 4 months old). i think it is just a phase. she only did it for about 2 weeks and then finally just started sleeping through the night and slepping in til about 8 like she was before. i say just stick it out and see what happens. i always made my daughter get her blankie from her room and have her lay on floor next to my bed and turn on a cartoon for her she would fall right back to sleep. i think its just a jealousy thing that the baby is gettin so much attention.

I would let her crawl in and stay. Unless she is seriously disturbing your sleep, or starts doing it an hour after you put her to bed. For now it is offering her comfort and a kind of bonding time which will help her adjust to her new sibling, and you both are getting needed sleep! For now, do what works, this is not the time to start a battle of wills.

my son did this also when his baby sister was brand new (he was 21 months when she was born). It was a phase that only lasted a week at the most. My husband would wake up with him so I could get more sleep though

My oldest did this too, it was a phase. If it works for you to get more sleep, don't worry about it. To avoid waking you up, you could even make a little bed for her next to yours and just tell her to crawl in there without waking you, or have her start her night there. Or let husband get a good night's rest in the guest room so he can go to work, and then you can go to bed when the 2 year old does with the baby in a bassinet, so you are all 3 in the same room. Pretty soon the 2 year old will realize that waking every 2 hours to a crying baby is no fun, and will probably go back to her own bed.
When there is a new baby, you just do what works for you. Or can hubby deal with the 2 year old and leave you sleeping? There are families that share a big bed until kids are quite large, so "normal" runs from strict sleeping alone in one's own bed from day 1 all the way to sleeping with mom and dad to the age where I think it sounds a little creepy (think of 2 queen sized beds next to each other with mom, dad and 2 kids in it until teen years - but it works for them).
If the nap time is allowing you some rest during the day, try to nap then too. I know it is hard to do, you can quickly throw in a load of wash or do some dishes, but they can wait. At this stage mom should nap when she can! Congratulations on your new little baby, and I hope you recover soon with much needed rest.

Kids go through all sorts of phases. I co-slept with my kids until they were about 2 (and generally the next one was on the way), and then gradually transitioned them to their own bed. But there were plenty of times that I let them crawl in with us in the early morning. I would suggest just being patient, she is probably seeking reassurance that she is still as loved and as important as she was before the baby came, and this is a little thing that helps her know she is.
Maybe some days you can cuddle with her, and others let her dad take that roll (and sometimes he can move her back to her bed).