Anonymous wrote:OP, I think we have the same nanny!

I face these exact same challenges and deciding which battles to pick is a regular issue for me.
Mostly I think you should try to let it go. 18 mths is a time of huge transition for kids but very soon your daughter will be testing limits (physical, behavioral, etc...) and may well need a fairly constant level of oversight just to keep her off the table tops or from leaving the house, or whatever. She'll also start developing more independence, and working on things like puzzles (that can by nature be more individual activities). So I think some of that will regulate itself. Also, if you're at all concerned about language development (not that I think you need to be given what you've described) then the solution to that is a lot of focussed one on one time - so maybe you could channel your nanny's natural inclinations to over-attentiveness in a way that at least addresses another concern you might have. Ask her to devote a chunk of time every day to language development work (whatever you choose). If you like, you could also find ipad apps (or something like that) that support what the nanny is doing, but also are solo game play type things (thereby encouraging a little more independence). We have alphabet apps that our twins play with and they love it (and it buys me 5 or 10 minutes.)
Anyway, overall I think you're right to carefully pick your battles. My nanny is the same way - I often wish she'd just let them fend for themselves a bit more, play independently (and let's not even discuss allowing them to cry at naptime!) etc... But I trust her completely, know that my kids are surrounded by genuine loving care all the time, she'd jump in front of a car for them, etc... I wouldn't trade that for the day to day differences that I figure won't matter at all in a couple of years.
Good luck. I regularly am amazed at how hard the nanny/mother relationship is - even when all parties are great, happy, supportive, etc...