Puberty advice - painful developing breasts

My 10 and a 1/2 year old daughter has recently within the last 3 or 4 days started to develop breast tissue - this is only on one side and is very tender for her.

IS there anything i can give her - naturally - to help ease this transition period??

I thought about Oil of evening primrose or starflower but thought id check first whether this would be suitable or if there is something more suitable (its a long time since i was at this stage and i dont remember having much tenderness)

Thanks in advance

(it doesnt seem like 2 minutes ago i was giving birth to her!!)