Is this something new for her? Or was she always sorta clingy?
Try getting the book "Your 4 year Old", "Your 3 Year Old", "Your 5 Year Old" etc. You can get it from www.amazon.com
It's a good book series describing EACH age-set and their characteristics. It's very useful, to give parents insights on their child. Each age has its quirks and blessings. But we can't always read their little minds. So this book helps.
Did she just turn 4 years old? Or has she been for awhile already? Or is she almost 5? The reason I ask, is that at each age juncture or age-change, children can become clingy or have "growing pains" which also include emotionally as well. So something to keep in mind.
Or, has she been under stress lately? Or a change in home life/school life/problems/recent traumas/ or anything you don't know about? These can also make a child more clingy.
Also though, a child's "bond" with their Mommy also changes and goes through transitions and evolves at each age change. I see this in my own daughter... who can be a REAL clingy little girl, although very independent overall.
I know it can be irritating and grating.... and hard. As a Mom, we don't like to feel irritated at our child... but MEGA clingy-ness can tweak us too. LOL
Anyway, have you just tried and talking with her? Maybe she is simply needing you more now, for whatever reason. Just talk and let her talk stream-of-thought kind of talking and don't correct her or judge her. Lots of time, little girls have SO many emotions and thoughts in their heads... and they want to connect with us. At least that is how my daughter is. So I always make a time for her to just let her talk about anything under the sun. And she just needs me more sometimes... depending on her moods.
My daughter is also like that... depending on her moods. She likes to touch me, hold my hand, hug, sit on me... etc. But well, that is the way she has always been. So in my case, it is not a new or different behavior for her. But as she's gotten older & per her maturity, I've just verbally talked to her about it. But the thing is, in school and most times, she is SO independent and a very confident little girl.
I don't have a real answer, just that I can relate and perhaps, try and find out what is bothering your daughter if anything...
All the best,