HELP? why can't i look her in the eye?

i'm 19 and male. whenever i visit my second cousin 23yo Lily, i always like to spend a lot of time with her daughter(my 7yo third cousin) Bell. but for some reason, i can never bare to look Bell in the eye for more than a few seconds. i don't know why, because i love playing with her, and just being around her makes me smile because she's so cute and cheery, it's adorable! X3 but when she looks me in the eye, idk, i just get this sudden urge to look away, and then i feel kinda embarrassed afterward. she eventually caught on and asked me about it, and i told her i didn't know either. i'm so attached to her too, whenever she talks i just wanna squeeze her tightly and say "AAAAAAWWWWWW!!!!!!!!!", i get pretty mad or jealous when other people try to see her, and it's really hard to tell her bye and leave once i've seen her. why do you think that is? and why can't i look her in the eyes without getting embarrassed?