Seeking Constructive Feedback

I have been an EMT and have also worked in an emergency room since 2007. Over time, I became the go to person for hard sticks in adults, babies and difficult to access patients. Even though I am very good at IV's, we all have our bad days were we are not able to get an IV even if the vein jumped out to help us! Everyone has their own technique and ways they like to start a line (sitting, setup, locating a vein).

Last evening while starting a line, the patients nurse (who is extremely nice) was telling me which vein to access, how to access it, how to hold the needle, tried to put the tegaderm on for me , tape the IV, etc. Internally I almost lost it. She then proceed to grab my hand and tell me "the way I like to do it is once I get a flash, I remove the needle and float the IV in". What? ?I understand you don't know my skill set, but you never insert yourself and surely don't hoover over and grab someone's hand unless asked. Needless to say, the vein blew. So then she says to me, "o well we can go into another room and practice". I politely said, "no that's OK, I don't need practice". I felt bad because I didn't say it in the most nice way, but I was very irritated and annoyed. She is literally hovering over my procedure space telling me how to start the IV!

So my question is, for those who have experienced working with someone new on shift who don't know your skill set, how do you politely let them know "Thank you, I know what I am doing, now back off" but yet be open to way they might do things?