The dilemma Recently my mother found a maths tutor for me (I’m in Year 12). He’s a 45-year-old guy who seems very likeable and knows his stuff. When our first lesson ended, my mother invited him to stay for tea, and then after the next one and the one after that … My mother is divorced.

He confessed to her a week ago that he is now in love with her and would like a relationship. Even before this, I told my mum, joking: “You guys seem to like each other.” She responded: “Why do you always assume I am in love? He is being nice and I am being nice back. That’s all.”

But then I walked into the room and my mum was on this guy’s lap. She noticed me, jumped off him and talked to me like normal. We ate together, but I couldn’t hide my disgust.

I’m angry with my mum and my tutor and feel it’s disrespectful towards me. The fact she said: “At least I jumped off him” and didn’t apologise made me really sad. She went out after that so I was left at home crying. I felt full of rage. I want to know if the way I felt and reacted was appropriate?

Mariella replies The simple answer is yes. It’s a tricky situation and so it’s no wonder you were upset and confused. Clearly you realised something was developing between them even before your mum knew, or before she wanted to admit to it. That doesn’t mean she was being deceitful. She was trying to protect you, but it hasn’t worked out like that.

Relationships are not predictable, especially at the beginning, and I bet your mum didn’t want to admit she had feelings for him because she didn’t know if it was going to develop into something serious. Most of us go out with a few different people before we find a person we have a chance of having a long-term relationship with, so there is always a trial period when nobody knows what is going to happen next.

That works OK when you are single because no one else is being upset by having to get to know different possible partners, and your choices aren’t being judged by someone you love a lot more than any new partner … your child.

I think we both have to understand from your mum’s point of view that with working and looking after you she doesn’t get much time to go out and meet people, certainly not as much time as she would have had before she had children. With this man your mum doesn’t have the chance of a trial period in which you could be kept ignorant, because he is in your house, where you are witness to whatever is happening. They weren’t out on a date.

Witnessing a parent finding a new partner can cause all sorts of problems for the child involved

That’s where you have a right to expect better. It’s not OK for her to put you in an embarrassing and awkward situation, which I think is what happened the other day. You are definitely justified in finding it uncomfortable that she is sitting on your tutor’s lap.

What’s important is that you don’t let it make you angry, but try and understand why it has upset you and then calmly talk it out with your mum. I’m sure she didn’t mean to offend you or upset you and I imagine she was just as distressed as you. Sometimes when we react emotionally it’s hard to take a minute to work out what we are feeling and why.

Witnessing a parent going through the motions of finding a new partner can cause all sorts of problems and you are not the first child to find themselves feeling disrespected and confused. Perhaps you should have another conversation with your mum about this when you are feeling calm. It’s certainly a good idea to tell her what that situation made you feel.

She has every right to have a life of her own. Hopefully she will meet someone and it’d be great if it was someone you liked as much as you say you do this man. It would be far better for everyone if she didn’t audition prospective partners in front of you. Maybe they will end up going out seriously, but until they are it is unfair and inappropriate for you to be exposed to their flirtation.

Maybe you should tell your mum that you are happy she has found such a likeable man, but that you would prefer, if they are going to be dating, to keep their relationship separate from your studies. It probably means finding another tutor, as that is the only way to make the situation less complicated. I don’t think your mum wants to be employing someone she is on the verge of dating, and it would work out best for all concerned if your tutoring was kept separate from your mum’s love life.

Maybe, if it all works out, you can get help with your maths from him because he is a committed adult in your life. But for now their relationship means you have a vacancy for maths instruction.

You asked if your behaviour was wrong and the simple answer is no it wasn’t. Watching a parent rebuild their romantic life is tricky for any child and you have every right to have your feelings to be respected. I’m sure your mum will agree when you put it to her reasonably.

If you have a dilemma, send a brief email to mariella.frostrup@observer.co.uk. Follow her on Twitter @mariellaf1