I kow this can be intimidating. Even without consciously doing it, someone with experience can project that experience out in a way that can put off the inexperienced.

Not sure what practical advise I can give save to reinforce that given above. Though one thing that may help:

When you are in play, make sure that you are definitely in play. She is not allowed to comment on what you are doing unless it is for safety reasons or prearranged safewords (if you use them). She has to agree to stay silent and obey all commands etc. Then, when play is over, maybe during afterplay or even a while after, you can talk about it. That is the time when she feedsback any opinions about your methods, when you could hit her harder, how far you could have gone and so on. This way you may get the benefit of her experience without you feeling like she is criticising your every move while you are trying to get into Domspace.