We found Holly slept much better once she was going into her cot in her room for naps - when she was tiny and used to nap in the lounge with us, she didnt sleep for long. Now she has naps (usually 3 a day) which are between 45 mins and 2 hours. Usually two 45 min ones and a 1.5/2 hour one.
My friends baby has 30 min naps a few times a day and he does fine. I think all babies are different, its just a case of working out what is good for yours.
Would def recommend trying her in her cot, see if it makes a difference. May take a few days for her to get used to napping there, but stick with it!