If you are uncomfortable, there is something wrong. I would work to make sure you are not in circumstances where you mother can be quite so physically intimate with you and I would not talk to her about your relationship with anyone else (since it is your and that person's relationship and does not involve your mother). When she makes you uncomfortable, tell her you do not enjoy whatever from her and stop her. Yes, she is important and mother, etc. but you do not enjoy/it conflicts with you. You can defend your choices, if you have to, by asking her if she wants to make you unhappy because feeling conflicted like that makes you unhappy.