Partner has inappropriate relationship at work

I am looking for some advice regarding my partners relationship with his receptionist at work, I am not able to talk to my mom or friends as I know they will worry and take my side which is not what I need - I need completely neutral opinions and advice. To cut a long story short this woman is a few years older than my partner (in her forties) and she seems to be obsessed with him. Last christmas there were 3 bag fulls of presents under the tree for him and his dog and cat from her, leaving me feeling quite awkward (but I didnt say anything as we hadnt been together for very long) The lavish present buying has continued and now she has moved onto our "baby to be" (I am 7 months pregnant) she keeps buying gifts for the baby and last week she gave £100 in an envelope to my partner for the baby then last night I got home and she has purchased 3 x "my first" harrods teddy bears which turned up in the post. She texts and emails him every weekend even though she sees him every day at work and now she puts him on a guilt trip saying "you used me" and "you dont need me anymore now you are in a relationship" I find her behaviour rather obsessive and last week I called her a "bunny boiler" and believe me it takes a lot for me to dislike someone I generally like everyone but this is really getting to me. She has also recieved some inheritance money and wishes to buy my partner a gift with this and keeps asking what he wants - it just seems like "buying affection" to me. He makes excuses for her saying she is lonely and that they are good friends and they were before i came along etc etc.....and I respond by saying "This is not normal behaviour - do you go around buying loads of presents for your friends and feel the need to keep in touch with them every day even though you see them every day at work" I have really tried to accept this relationship but the Harrods bears were the final straw and I was very down last night - he even said to me that he doesnt want to come home because of how i am behaving about it all!!!!. I think this may ruin our relationship if we are not careful i feel like I am being portrayed as the bad person here......any advice appreciated even if its just to tell me to accept this relationship and accept the gifts - it just doeant feel normal to me but maybe I am being over the top? thanks for reading.