Ok, I know you didn't BF but it is impossible for a baby to have an "obsession" as that implies that your little girl is capable of a thought that continually preoccupies or intrudes on her mind.

Your heart is also underneath your left breast, she will still want to snuggle in for warmth and comfort regardless of whether she was BF or not.

Yes its inconvenient when they are showing your boobs to complete strangers but do you honestly think she has the level of understanding that you seem to expect her to have? She is STILL just a baby! I don't expect my 2yo to have a real concept of "boobies out are a no no "

Maybe if you stop focussing on what she is doing and learn to relax a little and just move her hand away without making a big deal or telling her off she might loose interest.

Maybe if you give her "time" with them at a special time of day like nap time or if you have a bath with her and let her look and touch and you explain to her what they are etc when she gets a bit older

I never make a big deal out of my daughter touching my breasts or pulling down my top. If its not convenient I just say to her "I am sure X doesn't want to see mummies breasts, here why don't you play with this for a while" mind you she is also older than your DD so has more concept of what I am saying.

If you react badly to her and make her upset of course she will get clingier and want more snuggles and be closer to you for comfort and that for may mean hands down mummies top.

Nae